[gdk-pixbuf] tests: Disable running tests in parallel

[Bastien Nocera <hadess src gnome org>]

commit d64805f91cbd5e1db595234964423fbaa72d9cb8
Author: Bastien Nocera <hadess hadess net>
Date:   Thu Jul 13 12:19:16 2017 +0200

    tests: Disable running tests in parallel
    
    Some of the tests are _very_ memory intensive, so running two of them at
    the same time is probably ill-advised.

 tests/Makefile.am |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/tests/Makefile.am b/tests/Makefile.am
index f346217..8126c12 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -1,5 +1,7 @@
 include $(top_srcdir)/glib-tap.mk
 
+.NOTPARALLEL:
+
 AM_CPPFLAGS =                          \
        -I$(top_srcdir)                 \
        -I$(top_srcdir)/gdk-pixbuf      \