configure.ac: fix cross compilation

AC_CHECK_LIB seems to not work correctly with OpenWrt. Add possibility
to disable lz4 and lzo2 manually.

Fixes errors in the form of:
  Package f2fsck is missing dependencies for the following libraries:
  liblz4.so.1
  liblzo2.so.2

Signed-off-by: Nick Hainke <vincent@systemli.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
1 file changed