tools/CMakeLists: Use a macro for common code, fix custom_command output

[MatzeB]

Summary

Removing the explicit ${CMAKE_CURRENT_BINARY_DIR}/ prefix from the
add_custom_command OUTPUT part, fixes ninja warnings for me. I assume this is possible now after we chose a different target name for the add_custom_target().

This version works fine for me with ninja and make now. Does this look sensible and work for others?

[jlebar]

wfm with ninja. I don't (yet) know enough cmake to feel comfortable approving this patch, though.

[mcrosier]

LGTM. Works in both make and ninja as far as I can tell.

tools/CMakeLists.txt

 add_executable(timeit-target ${CMAKE_CURRENT_SOURCE_DIR}/timeit.c)
 
 # FIXME: Replicate Makefile.tools's logic for determining whether to use fpcmp/fpcmp.sh
 
 # Note that we have to compile fpcmp and timeit for the host machine even when
 # cross compiling to a different target. We use custom rules doing "cc file.c"
 # as an ad-hoc solution for now. A proper solution would probably be based on
 # ExternalProject_Add(); See also http://reviews.llvm.org/D15004
 
 set(TEST_SUITE_HOST_CC "cc" CACHE STRING "C compiler targetting the host")
 mark_as_advanced(TEST_SUITE_HOST_CC)
-add_custom_target(fpcmp-host
-    DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/fpcmp)
-add_custom_command(OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/fpcmp
-  COMMAND ${TEST_SUITE_HOST_CC} ${CMAKE_CURRENT_SOURCE_DIR}/fpcmp.c -o ${CMAKE_CURRENT_BINARY_DIR}/fpcmp
-  DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/fpcmp.c
-)
-add_custom_target(timeit-host
-    DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/timeit)
-add_custom_command(OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/timeit
-  COMMAND ${TEST_SUITE_HOST_CC} ${CMAKE_CURRENT_SOURCE_DIR}/timeit.c -o ${CMAKE_CURRENT_BINARY_DIR}/timeit
-  DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/timeit.c
+macro(llvm_add_host_executable targetname exename sourcefile)
+  add_custom_command(OUTPUT ${exename}
+    COMMAND ${TEST_SUITE_HOST_CC} ${CMAKE_CURRENT_SOURCE_DIR}/${sourcefile} -o ${CMAKE_CURRENT_BINARY_DIR}/${exename}
+    COMMENT "[TEST_SUITE_HOST_CC] Building host executable ${exename}"
+    DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/${sourcefile}
   )
+  add_custom_target(${targetname} DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/${exename})
+endmacro()
+
+llvm_add_host_executable(fpcmp-host fpcmp fpcmp.c)
+llvm_add_host_executable(timeit-host timeit timeit.c)