[compiler-rt][ARM] Fix filtering of ARM targets

[iid_iunknown]

Summary

Similarly to i686, the ARM build target has multiple names, such as armhf, armv7 and so on. Currently we get duplicated symbol definitions for these targets while compiling the library. Each duplicated definition has its generic version from lib/builtins and an ARM-specialized version from lib/builtins/arm.

This patch fixes filtering for ARM to ignore the generic definitions if they have their ARM specializations.

[iid_iunknown]

Thanks for reviewing this, Saleem!

lib/builtins/CMakeLists.txt

else ()
 
   foreach (arch ${BUILTIN_SUPPORTED_ARCH})
     if (CAN_TARGET_${arch})
       # NOTE: some architectures (e.g. i386) have multiple names.  Ensure that
       # we catch them all.
       set(_arch ${arch})
       if("${arch}" STREQUAL "i686")
         set(_arch "i386|i686")
+      elseif("${arch}" STREQUAL "armv6m")
+        set(_arch "arm|armv6m")
+      elseif("${arch}" MATCHES "^(armhf|armv7|armv7s|armv7k|armv7m|armv7em)$")
+        set(_arch "arm")
       endif()
 
       # Filter out generic versions of routines that are re-implemented in
       # architecture specific manner.  This prevents multiple definitions of the
       # same symbols, making the symbol selection non-deterministic.
       foreach (_file ${${arch}_SOURCES})
         if (${_file} MATCHES ${_arch}/*)
           get_filename_component(_name ${_file} NAME)