[CMake][compiler-rt] Treat target cflags as list rather than string

This is need after 30dfe016d4.

Differential Revision: https://reviews.llvm.org/D128548

compiler-rt/cmake/Modules/CompilerRTAIXUtils.cmake

@@ -11,7 +11,7 @@ set(linkopts
   # > On AIX, runtime linking is no longer enabled by default.
   # See https://cmake.org/cmake/help/latest/release/3.16.html
   if(${CMAKE_VERSION} VERSION_GREATER_EQUAL "3.16.0")
-    set(linkopts -Wl,-G ${linkopts})
+    list(PREPEND linkopts -Wl,-G)
   endif()
   set(${link_flags} ${linkopts} PARENT_SCOPE)
 endfunction()

compiler-rt/lib/fuzzer/CMakeLists.txt

@@ -141,7 +141,7 @@ if(OS_NAME MATCHES "Linux|Fuchsia" AND
     get_target_flags_for_arch(${arch} target_cflags)
     if(CMAKE_CXX_COMPILER_ID MATCHES Clang)
       get_compiler_rt_target(${arch} target)
-      set(target_cflags "--target=${target} ${target_cflags}")
+      list(PREPEND target_cflags --target=${target})
     endif()
     set(cxx_${arch}_merge_dir "${CMAKE_CURRENT_BINARY_DIR}/cxx_${arch}_merge.dir")
     file(MAKE_DIRECTORY ${cxx_${arch}_merge_dir})