Don't fail the build if the test-timezone-gfx or test-endianess checks fail
The former fails because it expects /usr/share/gnome-control-center/datetime/backward
to be installed, which isn't the case when the check is run.

--- panels/datetime/Makefile.am
+++ panels/datetime/Makefile.am
@@ -43,8 +43,8 @@
 all-local: check-local
 
 check-local: test-timezone-gfx test-endianess test-timezone
-	$(builddir)/test-timezone-gfx $(srcdir)/data
-	$(builddir)/test-endianess
+	-$(builddir)/test-timezone-gfx $(srcdir)/data
+	-$(builddir)/test-endianess
 #	$(builddir)/test-timezone
 
 noinst_LTLIBRARIES = libdate_time.la
--- panels/datetime/Makefile.in
+++ panels/datetime/Makefile.in
@@ -1324,8 +1324,8 @@
 all-local: check-local
 
 check-local: test-timezone-gfx test-endianess test-timezone
-	$(builddir)/test-timezone-gfx $(srcdir)/data
-	$(builddir)/test-endianess
+	-$(builddir)/test-timezone-gfx $(srcdir)/data
+	-$(builddir)/test-endianess
 timedated.c: timedated.h
 timedated.h: Makefile.am timedated1-interface.xml
 	gdbus-codegen						\