[compiler-rt] Handle non-canonical triples with new runtime lib layout

[ro]

Summary

As described in Issue #54196, the ideas of clang and compiler-rt where runtime libs are located with -DLLVM_ENABLE_RUNTIMES can differ. This is the compiler-rt side of the patch I've used to get them in sync for the amd64-pc-solaris2.11 and sparc64-unknown-linux-gnu release builds.

Tested on amd64-pc-solaris2.11 and sparc64-unknown-linux-gnu.

I don't expect this to be ready as is, just posting for reference.

[MaskRay]

Nice if we just need these lines to solve the problem.

Have you made some investigation whether this is the best place doing the normalization? Are there other places normalizing arch?

[ro]

In D133406#3781465, @MaskRay wrote:

Have you made some investigation whether this is the best place doing the normalization? Are there other places normalizing arch?

I did, and everything converged here. The fact that the Android i386 -> i686 normalization already happens here suggests that it's the right place.

compiler-rt/cmake/Modules/CompilerRTUtils.cmake

 function(get_compiler_rt_target arch variable)
   string(FIND ${COMPILER_RT_DEFAULT_TARGET_TRIPLE} "-" dash_index)
   string(SUBSTRING ${COMPILER_RT_DEFAULT_TARGET_TRIPLE} ${dash_index} -1 triple_suffix)
   if(COMPILER_RT_DEFAULT_TARGET_ONLY)
     # Use exact spelling when building only for the target specified to CMake.
     set(target "${COMPILER_RT_DEFAULT_TARGET_TRIPLE}")
   elseif(ANDROID AND ${arch} STREQUAL "i386")
     set(target "i686${triple_suffix}")
+  elseif(${arch} STREQUAL "amd64")
+    set(target "x86_64${triple_suffix}")
+  elseif(${arch} STREQUAL "sparc64")
+    set(target "sparcv9${triple_suffix}")
   else()
     set(target "${arch}${triple_suffix}")
   endif()
   set(${variable} ${target} PARENT_SCOPE)
 endfunction()
 
 function(get_compiler_rt_install_dir arch install_dir)
   if(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR AND NOT APPLE)