[gimp] app: Prevent parallel builds for the tests

[Michael Schumacher <schumaml src gnome org>]

commit c008ef7e85614064a695dcad5cd220399db0007e
Author: Michael Schumacher <schumaml gmx net>
Date:   Fri Jun 29 07:49:06 2018 +0000

    app: Prevent parallel builds for the tests
    
    The tests must not be run in parallel or in a different order as specified.

 app/tests/Makefile.am | 4 ++++
 1 file changed, 4 insertions(+)
---
diff --git a/app/tests/Makefile.am b/app/tests/Makefile.am
index b9be39c800..0cc075bb47 100644
--- a/app/tests/Makefile.am
+++ b/app/tests/Makefile.am
@@ -1,3 +1,7 @@
+# Prevent parallel builds for the tests, as e.g. done by make -j check
+# The tests must not be run in parallel or in a different order as specified
+.NOTPARALLEL
+
 SUBDIRS = \
        files           \
        gimpdir         \