[compiler-rt][AArch64] Put outline atomic helpers into dedicated dir.

[mstorsjo]

Looks sensible to me, thanks! (Didn't test it myself though.)

[mstorsjo]

Adding llvm-commits as subscriber to this one, as I guess it hasn't been visible on any mailing list yet.

compiler-rt/lib/builtins/CMakeLists.txt

 
 # Generate outline atomics helpers from lse.S base
 set(CUSTOM_FLAGS ${CMAKE_C_FLAGS})
 if(NOT ANDROID)
   append_list_if(COMPILER_RT_HAS_VISIBILITY_HIDDEN_FLAG -DVISIBILITY_HIDDEN CUSTOM_FLAGS)
 endif()
 append_list_if(COMPILER_RT_HAS_ASM_LSE -DHAS_ASM_LSE CUSTOM_FLAGS)
 string(REPLACE " " "\t" CUSTOM_FLAGS "${CUSTOM_FLAGS}")
+set(OA_HELPERS_DIR "${CMAKE_CURRENT_BINARY_DIR}/outline_atomic_helpers.dir")
+file(MAKE_DIRECTORY ${OA_HELPERS_DIR})
 
 foreach(pat cas swp ldadd ldclr ldeor ldset)
   foreach(size 1 2 4 8 16)
     foreach(model 1 2 3 4)
       if(pat STREQUAL "cas" OR NOT size STREQUAL "16")
-        set(helper_asm outline_atomic_${pat}${size}_${model}.S)
+        set(helper_asm ${OA_HELPERS_DIR}/outline_atomic_${pat}${size}_${model}.S)
         add_custom_command(
           OUTPUT ${helper_asm}
           COMMAND ${CMAKE_C_COMPILER} -E ${CUSTOM_FLAGS} -DL_${pat} -DSIZE=${size} -DMODEL=${model}
                   ${CMAKE_CURRENT_SOURCE_DIR}/aarch64/lse.S -o ${helper_asm}
           DEPENDS aarch64/lse.S assembly.h
         )
         set_source_files_properties(${helper_asm} PROPERTIES GENERATED TRUE)
         set(aarch64_SOURCES