[CMake] CMake flags to TRY_RUN

[James Bigler]

I have a some code that I need to test and I need to feed it a default 
set of compiler flags.  I'm trying to set CMAKE_C_FLAGS via the -D 
system to override the default ones CMake provides.

   SET(COMPILE_TEST_SOURCE ${CMAKE_BINARY_DIR}/test/compile-test.c)
   FILE(WRITE ${COMPILE_TEST_SOURCE} "int main() { return 0; }\n")\
   SET(ARCH "i686")
   MESSAGE("Testing ARCH = ${ARCH}")
   SET(ARCH_FLAG "-march=${ARCH} -mtune=${ARCH}")
   SET(COMPILER_ARGS "${ARCH_FLAG} ${C_FLAGS_RELEASE} ${C_FLAGS}")
   TRY_RUN(RUN_RESULT_VAR COMPILE_RESULT_VAR
     ${CMAKE_BINARY_DIR}/test ${COMPILE_TEST_SOURCE}
     CMAKE_FLAGS "-DCMAKE_C_FLAGS:STRING=${COMPILER_FLAGS}"
     OUTPUT_VARIABLE OUTPUT
     )
   MESSAGE("RUN_RESULT_VAR     = ${RUN_RESULT_VAR}")
   MESSAGE("COMPILE_RESULT_VAR = ${COMPILE_RESULT_VAR}")
   MESSAGE("OUTPUT             = ${OUTPUT}")

This builds and runs the code, but it has two problems.

1. My flags don't get passed in.
2. CMake later complains about my temporary file:

CMake Error: File 
/home/scinew/bigler/manta/trunk/opt-4.0.2/test/compile-test.c is written 
by WRITE_FILE (or FILE WRITE) command and should not be used as input to 
CMake. Please use CONFIGURE_FILE to be safe. Refer to the note next to 
FILE WRITE command.

I'm using cmake 2.4.6 and 2.2.3.

James