MFC r264794:

MFC r264794:
  Move xdev knobs from release/arm/release.sh and into an
  XDEV_FLAGS variable in ${KERNCONF}.conf file.

Local changes:
  Fix XDEV_FLAGS for stable/9 branch, in particular, remove
  all *_CLANG* knobs, and move WITH_GCC=1 to XDEV_FLAGS.
  This is effectively a no-op on stable/9, and merged for
  tracking purpose only.

Sponsored by:	The FreeBSD Foundation

git-svn-id: svn://svn.freebsd.org/base/stable/9@264960 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f