minor, turn AC_LANG_WERROR off permanently upon SXE_CHECK_LIBTOOL

Signed-off-by: Sebastian Freundt <freundt@fresse.org>
chore, follow-up, move libtool stuff further down ...

For one, we turn off AC_LANG_WERROR permanently after this, and
for another, XCCFLAG will be -XCClinker from here on.

Signed-off-by: Sebastian Freundt <freundt@fresse.org>
Merge branch 'bld/dist'

* bld/dist:
  chore, follow-up, move libtool stuff further down ...
  minor, turn AC_LANG_WERROR off permanently upon SXE_CHECK_LIBTOOL