[compiler-rt] Fix compilation when multiple architectures can be targeted

[evgeny777]

Summary

clang based toolchain can support all of arm, armhf and armv6m architectures which will break compilation of compiler-rt libraries when arm or armv6m is tested after armhf, because latter is adding --DCOMPILER_RT_ARMHF_TARGET.

[mstorsjo]

LGTM, I think this seems reasonable.

Maybe it'd be good to wait for a little while (e.g. one working day?) if someone else wants to comment something, but to me it seems correct.

compiler-rt/lib/builtins/CMakeLists.txt

else ()
   if(COMPILER_RT_BUILTINS_HIDE_SYMBOLS)
     append_list_if(COMPILER_RT_HAS_VISIBILITY_HIDDEN_FLAG VISIBILITY_HIDDEN BUILTIN_DEFS)
   endif()
 
   append_list_if(COMPILER_RT_HAS_ASM_LSE HAS_ASM_LSE BUILTIN_DEFS)
 
   foreach (arch ${BUILTIN_SUPPORTED_ARCH})
     if (CAN_TARGET_${arch})
+      set(BUILTIN_CFLAGS_${arch} ${BUILTIN_CFLAGS})
       # For ARM archs, exclude any VFP builtins if VFP is not supported
       if (${arch} MATCHES "^(arm|armhf|armv7|armv7s|armv7k|armv7m|armv7em|armv8m.main|armv8.1m.main)$")
         string(REPLACE ";" " " _TARGET_${arch}_CFLAGS "${TARGET_${arch}_CFLAGS}")
         check_compile_definition(__ARM_FP "${CMAKE_C_FLAGS} ${_TARGET_${arch}_CFLAGS}" COMPILER_RT_HAS_${arch}_VFP)
         if(NOT COMPILER_RT_HAS_${arch}_VFP)
           list(REMOVE_ITEM ${arch}_SOURCES ${arm_Thumb1_VFPv2_DP_SOURCES} ${arm_Thumb1_VFPv2_SP_SOURCES} ${arm_Thumb1_SjLj_EH_SOURCES})
         else()
           # Exclude any double-precision builtins if VFP is single-precision-only
if (CAN_TARGET_${arch})
       endif()
 
       # Remove a generic C builtin when an arch-specific builtin is specified.
       filter_builtin_sources(${arch}_SOURCES ${arch})
 
       # Needed for clear_cache on debug mode, due to r7's usage in inline asm.
       # Release mode already sets it via -O2/3, Debug mode doesn't.
       if (${arch} STREQUAL "armhf")
-        list(APPEND BUILTIN_CFLAGS -fomit-frame-pointer -DCOMPILER_RT_ARMHF_TARGET)
+        list(APPEND BUILTIN_CFLAGS_${arch} -fomit-frame-pointer -DCOMPILER_RT_ARMHF_TARGET)
       endif()
 
       # For RISCV32, we must force enable int128 for compiling long
       # double routines.
       if("${arch}" STREQUAL "riscv32")
-        list(APPEND BUILTIN_CFLAGS -fforce-enable-int128)
+        list(APPEND BUILTIN_CFLAGS_${arch} -fforce-enable-int128)
       endif()
 
       add_compiler_rt_runtime(clang_rt.builtins
                               STATIC
                               ARCHS ${arch}
                               SOURCES ${${arch}_SOURCES}
                               DEFS ${BUILTIN_DEFS}
-                              CFLAGS ${BUILTIN_CFLAGS}
+                              CFLAGS ${BUILTIN_CFLAGS_${arch}}
                               PARENT_TARGET builtins)
     endif ()
   endforeach ()
 endif ()
 
 option(COMPILER_RT_BUILD_STANDALONE_LIBATOMIC
   "Build standalone shared atomic library."
   OFF)