linphone: Disable building with -Werror

Pass --disable-strict to avoid having -Werror in CFLAGS.
Having -Werror in CFLAGS can lead to build problems depending
on the gcc version that is being used and it should not be used
in released code.

Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>