Backport change from glibc upstream that defines RELEASE as stable
instead of release. This will at least cause the default_cflags to be
set to expected default values again.
Ref issue #1396, although the bigger issue of respecting crosstool-ng
CT_GLIBC_EXTRA_CFLAGS is most likely still not fixed.
Signed-off-by: Hans-Christian Noren Egtvedt <hegtvedt@cisco.com>
