Always call $(top_srcdir)/tools/checkAPIs.pl with -sourcedir=$(srcdir)
from Makefile.am to allow out-of-source 'make checkapi'.
Change-Id: I60d7e0079984a8ededdacf4517a0738486fa7973
Reviewed-on: https://code.wireshark.org/review/1294
Reviewed-by: Anders Broman <a.broman58@gmail.com>