Fix the ALSA=OFF build after r402530.

Both extrapatch-no_alsa and patch-git_d6927712 touch the same region of
CMakeLists.txt, and the latter was failing to apply when the ALSA option was
disabled.

Fix it by keeping patch-git_d6927712 (which fixes the CFLAGS values
regardless of the value of the ALSA option) and replacing extrapatch-no_alsa
with some post-patch/post-configure changes that achieve the same end
result.

PR: 204858
MFH: 2015Q4