glibc-external: obey localedir

Signed-off-by: Christopher Larson <chris_larson@mentor.com>
tcmode: use ?= for locale vars

Signed-off-by: Christopher Larson <chris_larson@mentor.com>
gcc-runtime-external: use BINV in a few places to fix FILES

Signed-off-by: Christopher Larson <chris_larson@mentor.com>