[GSoC - x86_64 - automake] Limit CFLAGS to specific source for librtemsbsp.a

[Amaan Cheval]

Hi Chris!

I currently have code like this in c/src/lib/libbsp/x86_64/amd64/Makefile.am:

    librtemsbsp_a_SOURCES +=
../../../../../../bsps/x86_64/amd64/interrupts/handlers.c
    # XXX: Needed to use GCC "interrupt" attribute directives - can we
pass these
    # flags only for the handlers.c source file (compile to an object
file first and
    # then link with the rest for librtemsbsp.a?)
    librtemsbsp_a_CFLAGS = -mgeneral-regs-only

The CFLAGS arg is required to allow us to use
"__attribute__((interrupt))" to setup interrupt handlers in C. (See
[1] and ctrl+f "interrupt" for more.)

Is there a way to not force the CFLAGS for _all_ of librtemsbsp, but
to limit it only to handlers.c?

If not, is the above code something that would be acceptable to have upstream?

[1] https://gcc.gnu.org/onlinedocs/gcc/x86-Function-Attributes.html#x86-Function-Attributes