Fix installcheck case for tap tests

Author: adunstan

src/Makefile.global.in

@@ -317,7 +317,7 @@ endef
 ifeq ($(enable_tap_tests),yes)
 
 define prove_installcheck
-cd $(srcdir) && TESTDIR='$(CURDIR)' PATH="$(bindir):$$PATH" PGPORT='6$(DEF_PGPORT)' $(PROVE) $(PG_PROVE_FLAGS) $(PROVE_FLAGS) t/*.pl
+cd $(srcdir) && TESTDIR='$(CURDIR)' PATH="$(bindir):$$PATH" PGPORT='6$(DEF_PGPORT)' top_builddir='$(CURDIR)/$(top_builddir)' $(PROVE) $(PG_PROVE_FLAGS) $(PROVE_FLAGS) t/*.pl
 endef
 
 define prove_check