Applying the fopen fixup to override.m4 and rebuilding the autotools
update patch set made it clear that override.m4 wasn't consistently
included everywhere in binutils+gdb yet.
I used m4_include instead of m4_sinclude so that we'd learn about
failures to include. Unfortunately, m4 inclusion doesn't work the
way C '#include "sub/file"' works (starting relative from the current
file) so that a sinclude would silently fail if a configure.in file were
added that wasn't in a direct subdir of sim (due to the then-wrong
relative paths).
OK to squash this additional change in (or just commit it before the
patch set)?