[compiler-rt] CMake build: if LLVM_BUILD_32_BITS is on, then -m32 is added to llvm definitions. Let us override this by explicitly adding -m64 compiler flag when building compiler-rt libraries for x86_64 target

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@161415 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 97835a1..d8985c2 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -21,7 +21,7 @@
 
 # Detect whether the current target platform is 32-bit or 64-bit, and setup
 # the correct commandline flags needed to attempt to target 32-bit and 64-bit.
-if(CMAKE_SIZEOF_VOID_P EQUAL 4)
+if(CMAKE_SIZEOF_VOID_P EQUAL 4 OR LLVM_BUILD_32_BITS)
   set(TARGET_X86_64_CFLAGS "-m64")
   set(TARGET_I386_CFLAGS "")
 else()