Merge bitcoin/bitcoin#33857: doc: Add x86_64-w64-mingw32ucrt triplet to depends/README.md

ec8eb013a9 doc: Add `x86_64-w64-mingw32ucrt` triplet to `depends/README.md` (Hennadii Stepanov)
48496caa12 ci: Remove redundant `DEP_OPTS` from “Windows-cross UCRT” job (Hennadii Stepanov)

Pull request description:

  This PR is part of the ongoing effort to migrate to the modern UCRT runtime for cross-compiled Windows binaries, including release builds.

  For more details about this migration, see:
  - https://github.com/bitcoin/bitcoin/issues/30210
  - https://github.com/bitcoin/bitcoin/pull/33593
  - https://github.com/bitcoin/bitcoin/pull/33764

  Can be tested on the following systems:
  -  Debian Trixie x86_64 (requires the [`g++-mingw-w64-ucrt64`](https://packages.debian.org/trixie/g++-mingw-w64-ucrt64) package, as documented).
  -  Fedora 42 or 43 (requires the [`ucrt64-gcc-c++`](https://packages.fedoraproject.org/pkgs/mingw-gcc/ucrt64-gcc-c++/) package).

  Also see related upstream issues:
  - https://bugs.launchpad.net/ubuntu/+source/gcc-mingw-w64/+bug/2132114
  - https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1121403

ACKs for top commit:
  m3dwards:
    ACK ec8eb013a9
  hodlinator:
    ACK ec8eb013a9

Tree-SHA512: 26e6e0354fedd8cc79d186b519124c306a7de328ced7247804c6e6d546e9c71cd5b92af878ab0f9a3c1e506a339944acaeb0ac99cd56bed896fd77b952788ae0

ci/test/00_setup_env_win64.sh

@@ -9,7 +9,6 @@ export LC_ALL=C.UTF-8
 export CONTAINER_NAME=ci_win64
 export CI_IMAGE_NAME_TAG="mirror.gcr.io/debian:trixie"  # Check that https://packages.debian.org/trixie/g++-mingw-w64-ucrt64 can cross-compile
 export HOST=x86_64-w64-mingw32ucrt
-export DEP_OPTS="CC=${HOST}-gcc CXX=${HOST}-g++"
 export PACKAGES="g++-mingw-w64-ucrt64 nsis"
 export RUN_UNIT_TESTS=false
 export RUN_FUNCTIONAL_TESTS=false

depends/README.md

@@ -122,7 +122,8 @@ Common `host-platform-triplet`s for cross compilation are:
 
 - `i686-pc-linux-gnu` for Linux x86 32 bit
 - `x86_64-pc-linux-gnu` for Linux x86 64 bit
-- `x86_64-w64-mingw32` for Win64
+- `x86_64-w64-mingw32` for Windows using MSVCRT
+- `x86_64-w64-mingw32ucrt` for Windows using UCRT
 - `x86_64-apple-darwin` for Intel macOS
 - `arm64-apple-darwin` for ARM macOS
 - `arm-linux-gnueabihf` for Linux ARM 32 bit
@@ -144,10 +145,14 @@ proceeding with a cross-compile. Under the depends directory, create a
 subdirectory named `SDKs`. Then, place the extracted SDK under this new directory.
 For more information, see [SDK Extraction](../contrib/macdeploy/README.md#sdk-extraction).
 
-#### For Win64 cross compilation
+#### For Windows cross compilation using MSVCRT
 
     apt install g++-mingw-w64-x86-64-posix
 
+#### For Windows cross compilation using UCRT
+
+    apt install g++-mingw-w64-ucrt64
+
 #### For linux (including i386, ARM) cross compilation
 
 Common linux dependencies: