LLVMFlang: Add support for targeting MSVC ABI on Windows

The compiler does not yet support everything needed to integrate well with the MSVC ABI, in particular for runtime library selection and debug format selection. Document them in FIXME comments and leave this support undocumented by CMake for now.

Fixes: #24840 (closed)
Inspired-by: @pbo-linaro
Backport: release
Supersedes: !8776 (closed)

changed milestone to %3.28.0

added comp:llvmflang workflow:in-review labels

assigned to @brad.king

added 6 commits

• ef997aab - CMakeParseImplicitLinkInfo: Detect link lines using MSVC link.exe
• d05e7ffd - CMakeDetermineCompilerABI: Add option to skip implicit link info parsing
• fb6c1e3d - Fortran: Save CMAKE_LINKER variable persistently for MSVC ABI
• e9da436c - Tests: Enable CMP0091/CMP0141 for MSVC settings in FortranOnly test
• 8998398f - LLVMFlang: Add support for CMAKE_Fortran_COMPILER_TARGET
• 85af0b81 - LLVMFlang: Add support for targeting MSVC ABI on Windows

Compare with previous version

added lang:fortran label

mentioned in issue #24840 (closed)

mentioned in merge request !8776 (closed)

@pbo-linaro this implementation passes all the Fortran tests in CMake's test suite. Please try it out.

added 6 commits

• f08a4d9c - CMakeParseImplicitLinkInfo: Detect link lines using link.exe and lld-link
• f93fa043 - CMakeDetermineCompilerABI: Add option to skip implicit link info parsing
• cccd12e3 - Fortran: Save CMAKE_LINKER variable persistently for MSVC ABI
• 5b5cd94b - Tests: Enable CMP0091/CMP0141 for MSVC settings in FortranOnly test
• 2a67896d - LLVMFlang: Add support for CMAKE_Fortran_COMPILER_TARGET
• b9554992 - LLVMFlang: Add support for targeting MSVC ABI on Windows

Compare with previous version

We should resolve the open discussions before merging this, but meanwhile I'll stage this to see how the changes do in nightly testing.

Do: stage

added triage:blocked workflow:nightly-testing labels and removed workflow:in-review label

added 6 commits

• 12733d0d - CMakeParseImplicitLinkInfo: Detect link lines using link.exe and lld-link
• 7571e653 - CMakeDetermineCompilerABI: Add option to skip implicit link info parsing
• 9d060b86 - Fortran: Save CMAKE_LINKER variable persistently for MSVC ABI
• 26fa048f - Tests: Enable CMP0091/CMP0141 for MSVC settings in FortranOnly test
• e9af7b96 - LLVMFlang: Add support for CMAKE_Fortran_COMPILER_TARGET
• b9d70abc - LLVMFlang: Add support for targeting MSVC ABI on Windows

Compare with previous version

Do: stage

added 1 commit

• 26bf32cd - LLVMFlang: Add support for targeting MSVC ABI on Windows

Compare with previous version

Do: stage

resolved all threads

changed the description

removed triage:blocked label

Warnings:

• Eligible for the 3.28.x branch.

The warnings do not need to be fixed, but it is recommended to do so.