Copy and adapt code from mach/{i386,m68020}/ncg/mach.c to pass the
debugging stabs from EM to assembly. The next tools (as, led, cv)
already know how to put the stabs in the Mach-o executable.
Modify the function prolog/prologue so gdb uses fp, not sp, for N_LSYM
and N_PSYM stabs. Simplify prolog() by reducing differences between
stabs and no stabs, and zero and nonzero framesize. For files without
stabs, the new prolog has the same number of instructions and memory
accesses as the old prolog, and to run at about the same speed on my
PowerPC Mac.
This is enough to see some info for global and local variables in gdb
for Mac OS X. I still can't get a backtrace; gdb gets confused
because EM and ncg don't link 0(sp) to the previous stack frame.
I don't expect `ack -mlinuxppc -g` to work with gdb for Linux, because
we prepend underscores to the symbol table, which is correct for
Mach-o but wrong for ELF.
7c9c4f82fd