This was added to specify -Wa,-gdwarf2 when compiling the assembly
files. Considering the size of these .S files, it seems unnecessary
overkill and complicates the build system. All but one of these
compile down to 6 or fewer lines, and those hardly need extra debug
for anyone who is poking msp430 assembly. The 1 file that is larger
than that (crt_move_highdata.S) is still <15 insns.
This will also simplify merging it into the top-level Makefile.