Helmut Grohne authored Dec 21, 2017 and Adam Jackson committed Jan 08, 2018

When cross compiling, the value of MONOTONIC_CLOCK would be "cross
compiling", because AC_RUN_IFELSE doesn't work. However when enabling
wayland, a monotonic clock is required and configure aborts.

We change detection of CLOCK_MONOTONIC to degrade it gracefully from a
run check to a declaration check in case of cross compilation based on
the assumption that most systems will have a monotonic clock and those
that don't won't be able to run Xwayland anyway. The trade-off
essentially is either "always fail cross compilation" or "produce an
unusable Xwayland for unusual platform" and this commit switches to the
latter.

Signed-off-by: Helmut Grohne <helmut@subdivi.de>
Bug-Debian: https://bugs.debian.org/882531


Reviewed-by: Adam Jackson <ajax@redhat.com>