orbit2: fix build after automake 1.13.4 update

fixes:
| test/everything/Makefile.am:81: error: using '$(srcdir)' in TESTS is currently broken: '$(srcdir)/test.sh'
| test/inhibit/Makefile.am:4: warning: 'INCLUDES' is the old name for 'AM_CPPFLAGS' (or '*_CPPFLAGS')
| test/poa/Makefile.am:1: warning: 'INCLUDES' is the old name for 'AM_CPPFLAGS' (or '*_CPPFLAGS')
| autoreconf: automake failed with exit status: 1
| ERROR: autoreconf execution failed.
| WARNING: /home/superandy/tmp/oe-core-eglibc/work/x86_64-linux/orbit2-native/2.14.19-r0/temp/run.do_configure.14800:1 exit 1 from
|   exit 1
| ERROR: Function failed: do_configure (log file is located at /home/superandy/tmp/oe-core-eglibc/work/x86_64-linux/orbit2-native/2.14.19-r0/temp/log.do_configure.14800)
ERROR: Task 6208 (virtual:native:/home/superandy/data/oe-core/sources/meta-openembedded/meta-gnome/recipes-gnome/orbit2/orbit2_2.14.19.bb, do_configure) failed with exit code '1'

Signed-off-by: Andreas Müller <schnitzeltony@googlemail.com>
Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>