Now that we use AC_NO_EXECUTABLES, and we require a recent version of
autoconf, we don't need to define our own copies of these macros. So
switch to the standard AC_PROG_CC.
This logic was added to libc & libm to get it working again after some
reworks in the CPP handling, but now that that's settled, let's move
this to the common newlib configure logic. This will make it easier
to consolidate all the configure calls into the top-level newlib dir.
This does create a lot of noise in the generate scripts, but that's
because of the ordering of the calls, not because of correctness. We
will try to draw that back down in follow up commits as we modernize
the toolchain calls in here.
This matches what the other GNU toolchain projects have done already.
The generated diff in practice isn't terribly large. This will allow
more use of subdir local.mk includes due to fixes & improvements that
came after the 1.11 release series.
The newlib & libgloss dirs are already generated using autoconf-2.69.
To avoid merging new code and/or accidental regeneration using diff
versions, leverage config/override.m4 to pin to 2.69 exactly. This
matches what gcc/binutils/gdb are already doing.
The README file already says to use autoconf-2.69.
To accomplish this, it's just as simple as adding -I flags to the
top-level config/ dir when running aclocal. This is because the
override.m4 file overrides AC_INIT to first require the specific
autoconf version before calling the real AC_INIT.
