libglib2: remove fix-clock-gettime patch

This patch was introduced in 0ec42981
to fix a problem in libglib configure script when using the
configuration cache.

However, we decided that the shared configuration cache cannot work
reliably, to disable it by default, and probably to remove it
altogether. So just drop this patch, and don't autoreconfigure
libglib.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>