Fix c compile flags.

C Flags set in src and test directories were not getting set because
they were assigned to C_FLAGS, which is ignored. Changed to CFLAGS,
which is used by cmake to set default c compilation options.

firmware/asdf/src/CMakeLists.txt

@@ -8,7 +8,7 @@ temporary_config_file(${ASDF_SRC_DIR}/Arch/asdf_arch_${ARCH}.c ${CMAKE_CURRENT_B
 temporary_config_file(${ASDF_SRC_DIR}/Keymaps/asdf_all_keymap_defs_${KEYMAP}.h ${CMAKE_CURRENT_BINARY_DIR}/asdf_keymap_defs.h)
 
 
-list(APPEND C_FLAGS
+list(APPEND CFLAGS
   -std=c99
   -Wall
   -funsigned-char

firmware/asdf/test/CmakeLists.txt

@@ -3,7 +3,7 @@ configure_file(${ASDF_SRC_DIR}/Arch/asdf_arch_test.c asdf_arch.c)
 configure_file(${ASDF_SRC_DIR}/Arch/asdf_arch_test.h asdf_arch.h)
 
 
-list(APPEND C_FLAGS
+list(APPEND CFLAGS
   "-std=c99"
   "-Wall"
   "-Wextra"