Support for building universal x86 / Apple Silicon (arm64) app

This adds support for building MacVim as a fat binary (aka universal
app) for x86_64 / arm64 in CI.

The main challenge mostly lies in configuring the scripting language
default search paths for the libraries, and linking against gettext.
There are two possible approaches:
1. configure/build each arch completely separately, and then use `lipo`
   to stitch them back together. This is pretty annoying to set up, and
   kind of manual to do, and requires building the same thing twice,
   which is not great.
2. Build once with `--with-macarchs="x86_64 arm64` flag, which is what
   we do here.

gettext: Homebrew doesn't support fat binaries, and we also need to
build a custom x86 version of gettext to support down to macOS 10.9
anyway, so we manually download the bottle for arm64 gettext bottle, and
then stitch it with the x86 version to create a unified binary under
/usr/local/lib. This way we can just link against it in one go.

Scripting languages: Add new ifdef's to load different libs under
different architecture. Modify configure to support that (instead of
hacking a patch in during CI like Ruby). This means while on x86_64 it
will look under /usr/local/lib for Python 3, on arm64 it will look under
/opt/homebrew instead (this is the recommended path for Homebrew
installs for native arm64 packages). This new path is very specific to
Homebrew which is not ideal, but we could change this later and maybe
make the default search path logic for scripting languages smarter.

Note that since there is no arm64 in CI right now, this just builds the
app, but there will be no automatic testing to make sure it actually
works.

This is part of #1136.

.github/workflows/ci-macvim.yaml

@@ -18,7 +18,10 @@ env:
   vi_cv_dll_name_perl: /System/Library/Perl/5.18/darwin-thread-multi-2level/CORE/libperl.dylib
   vi_cv_dll_name_python: /System/Library/Frameworks/Python.framework/Versions/2.7/Python
   vi_cv_dll_name_python3: /usr/local/Frameworks/Python.framework/Versions/3.9/Python
+  vi_cv_dll_name_python3_arm64: /opt/homebrew/Frameworks/Python.framework/Versions/3.9/Python
   vi_cv_dll_name_ruby: /usr/local/opt/ruby/lib/libruby.dylib
+  vi_cv_dll_name_ruby_arm64: /opt/homebrew/opt/ruby/lib/libruby.dylib
+  vi_cv_dll_name_lua_arm64: /opt/homebrew/lib/liblua.dylib
 
   VIM_BIN: src/MacVim/build/Release/MacVim.app/Contents/MacOS/Vim
   MACVIM_BIN: src/MacVim/build/Release/MacVim.app/Contents/MacOS/MacVim
@@ -38,18 +41,27 @@ jobs:
         - os: macos-10.15
           xcode: 11.7
         - os: macos-10.15
-          publish: true
         - os: macos-11.0
+          publish: true
 
     runs-on: ${{ matrix.os }}
 
     steps:
       - uses: actions/checkout@v2
 
-      # Set up and install gettext for localization.
+      # Set up, install, and cache gettext library for localization.
+      #
       # Instead of using the default binary installed by Homebrew, need to build our own because gettext is statically
       # linked in MacVim, and need to be built against MACOSX_DEPLOYMENT_TARGET to ensure the built binary will work on
       # supported macOS versions.
+      #
+      # In addition, to support building a universal MacVim, we need an arm64 version of gettext as well in order to
+      # create a universal gettext binary to link against (Homebrew only distributes thin binaries and therefore this
+      # has to be done manually). To do that, we will just pull the bottle directly from Homebrew and patch it in using
+      # lipo. We can't use normal brew commands to get the bottle because brew doesn't natively support cross-compiling
+      # and we are running CI on x86_64 Macs. We also don't need to worry about the min deployment target fix on arm64
+      # because all Apple Silicon Macs have to run on macOS 11+.
+
       - name: Set up gettext
         if: matrix.publish
         run: |
@@ -71,11 +83,12 @@ jobs:
           brew uninstall --ignore-dependencies gettext
 
       - name: Cache gettext
+        id: cache-gettext
         if: matrix.publish
         uses: actions/cache@v2
         with:
           path: /usr/local/Cellar/gettext
-          key: gettext-homebrew-cache-${{ runner.os }}-${{ hashFiles('gettext.rb') }}
+          key: gettext-homebrew-cache-patched-unified-${{ hashFiles('gettext.rb') }}
 
       - name: Install gettext
         if: matrix.publish
@@ -85,6 +98,37 @@ jobs:
           brew install -s gettext.rb  # This will be a no-op if gettext was cached
           brew link gettext           # If gettext was cached, this step is necessary to relink it to /usr/local/
 
+      - name: Create universal gettext with arm64 bottle
+        if: matrix.publish && steps.cache-gettext.outputs.cache-hit != 'true'
+        env:
+          HOMEBREW_NO_AUTO_UPDATE: 1
+        run: |
+          set -o verbose
+
+          # Manually download and extract gettext bottle for arm64
+          gettext_url=$(brew info --json gettext | ruby -rjson -e 'j = JSON.parse(STDIN.read); puts j[0]["bottle"]["stable"]["files"]["arm64_big_sur"]["url"]')
+          gettext_ver=$(brew info --json gettext | ruby -rjson -e 'j = JSON.parse(STDIN.read); puts j[0]["versions"]["stable"]')
+
+          mkdir gettext_download
+          cd gettext_download
+          wget --no-verbose ${gettext_url}
+          tar xf gettext*.tar.gz
+
+          # Just for diagnostics, print out the old archs. This should be a thin binary (x86_64)
+          lipo -info /usr/local/lib/libintl.a
+          lipo -info /usr/local/lib/libintl.dylib
+
+          # Create a universal binary by patching the custom built x86_64 one with the downloaded arm64 one.
+          # Modify the actual binaries in /usr/local/Cellar instead of the symlinks to allow caching to work.
+          lipo -create -output /usr/local/Cellar/gettext/${gettext_ver}/lib/libintl.a /usr/local/Cellar/gettext/${gettext_ver}/lib/libintl.a ./gettext/${gettext_ver}/lib/libintl.a
+          lipo -create -output /usr/local/Cellar/gettext/${gettext_ver}/lib/libintl.dylib /usr/local/Cellar/gettext/${gettext_ver}/lib/libintl.dylib ./gettext/${gettext_ver}/lib/libintl.dylib
+
+          # Print out the new archs and verify they are universal with 2 archs.
+          lipo -info /usr/local/lib/libintl.a | grep 'x86_64 arm64'
+          lipo -info /usr/local/lib/libintl.dylib | grep 'x86_64 arm64'
+
+      # Set up remaining packages and tools
+
       - name: Install packages
         if: matrix.publish
         env:
@@ -101,6 +145,8 @@ jobs:
           sudo xcode-select -s /Applications/Xcode_${{ matrix.xcode }}.app/Contents/Developer
           xcode-select -p
 
+      # All set up steps are done. Build and test MacVim below.
+
       - name: Configure
         run: |
           set -o verbose
@@ -111,7 +157,6 @@ jobs:
             --with-tlib=ncurses
             --enable-cscope
             --enable-gui=macvim
-            --with-macarchs=x86_64
             --with-compiledby="GitHub Actions"
           )
           if ${{ matrix.publish == true }}; then
@@ -122,6 +167,11 @@ jobs:
               --enable-rubyinterp=dynamic
               --enable-luainterp=dynamic
               --with-lua-prefix=/usr/local
+              --with-macarchs="x86_64 arm64"
+            )
+          else
+            CONFOPT+=(
+              --with-macarchs=x86_64
             )
           fi
           echo "CONFOPT: ${CONFOPT[@]}"
@@ -140,6 +190,12 @@ jobs:
           grep -q -- "-DDYNAMIC_PYTHON3_DLL=\\\\\"${vi_cv_dll_name_python3}\\\\\"" src/auto/config.mk
           grep -q -- "-DDYNAMIC_RUBY_DLL=\\\\\"${vi_cv_dll_name_ruby}\\\\\"" src/auto/config.mk
 
+          # Also search for the arm64 overrides for the default library locations, which are different from x86_64
+          # because Homebrew puts them at a different place.
+          grep -q -- "-DDYNAMIC_PYTHON3_DLL_ARM64=\\\\\"${vi_cv_dll_name_python3_arm64}\\\\\"" src/auto/config.mk
+          grep -q -- "-DDYNAMIC_RUBY_DLL_ARM64=\\\\\"${vi_cv_dll_name_ruby_arm64}\\\\\"" src/auto/config.mk
+          grep -q -- "-DDYNAMIC_LUA_DLL_ARM64=\\\\\"${vi_cv_dll_name_lua_arm64}\\\\\"" src/auto/config.mk
+
       - name: Show configure output
         run: |
           cat src/auto/config.mk
@@ -185,12 +241,11 @@ jobs:
             echo 'Found external dynamic linkage!'; false
           fi
 
-          # Make sure we are building x86_64 only. arm64 builds don't work properly now, so we don't want to accidentally build
-          # it as it will get prioritized by Apple Silicon Macs.
+          # Make sure we are building universal x86_64 / arm64 builds and didn't accidentally create a thin app.
           check_arch() {
             local archs=($(lipo -archs "$1"))
-            if [[ ${archs[@]} != x86_64 ]]; then
-              echo "Found unexpected arch(s) in $1: ${archs[@]}"; false
+            if [[ ${archs[@]} != "x86_64 arm64" ]]; then
+              echo "Wrong arch(s) in $1: ${archs[@]}"; false
             fi
           }
           check_arch "${VIM_BIN}"