Fix Assembler test to parse C flags string before using

Commit 1f6c6b1c (use CMAKE_C_FLAGS when generating the assembler file,
2011-03-03) added use of CMAKE_C_FLAGS to the assembler generation step.
However, this variable is meant for direct substitution into a shell
command line so we need to parse it to separate the arguments first.

Tests/Assembler/CMakeLists.txt

@@ -7,7 +7,9 @@ set(SRCS)
 # and also generate assembler files from C:
 if("${CMAKE_GENERATOR}" MATCHES "Makefile")
   if(("${CMAKE_C_COMPILER_ID}" MATCHES "^(GNU|HP|SunPro|XL)$") OR ("${CMAKE_C_COMPILER_ID}" STREQUAL "Intel"  AND  UNIX))
-    execute_process(COMMAND ${CMAKE_C_COMPILER} ${CMAKE_C_FLAGS} -S "${CMAKE_CURRENT_SOURCE_DIR}/main.c" -o "${CMAKE_CURRENT_BINARY_DIR}/main.s")
+    set(C_FLAGS "${CMAKE_C_FLAGS}")
+    separate_arguments(C_FLAGS)
+    execute_process(COMMAND ${CMAKE_C_COMPILER} ${C_FLAGS} -S "${CMAKE_CURRENT_SOURCE_DIR}/main.c" -o "${CMAKE_CURRENT_BINARY_DIR}/main.s")
     set(SRCS "${CMAKE_CURRENT_BINARY_DIR}/main.s")
   endif(("${CMAKE_C_COMPILER_ID}" MATCHES "^(GNU|HP|SunPro|XL)$") OR ("${CMAKE_C_COMPILER_ID}" STREQUAL "Intel"  AND  UNIX))
 endif("${CMAKE_GENERATOR}" MATCHES "Makefile")