BaseTools GCC: move -c compiler flag to build rules

BaseTools GCC: move -c compiler flag to build rules

In order to be able to share the compiler flags with the linker (which
is required for LTO since it involves the linker doing code generation
based on the LTO bytecode), move the -c GCC argument to the build rules,
and drop it from the GCC CC_FLAGS definitions in tools_def.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Liming Gao <liming.gao@intel.com>