This should have no functionality change, but is supposed to keep us from
accidentally relying on the "full" Clang importer when in a backend job.
I tested it by archiving a little iOS app from a developer.
Unfortunately, part of the motivation here was that we'd get error messages when
we pass something Clang doesn't like, and that doesn't seem to be happening.
rdar://problem/21389553
Swift SVN r30407
Move helper function EmbedBitcode() from frontend_main.cpp to IRGen.cpp so we
can call it from performIRGeneration when the input file is Swift.
Add testing case to make sure that -embed-bitcode-marker option adds an
empty LLVM bitcode section.
rdar://19048891
Swift SVN r25577
With -embed-bitcode, save a copy of the llvm IR as data in the __LLVM,__bitcode
section and save the command-line options in the __LLVM,__cmdline section.
rdar://19048891
Swift SVN r25560
