[gupnp-dlna] build: Fix unit tests to use new automake parallel test harness

[Jens Georg <jensgeorg src gnome org>]

commit e7afa126c0c8154e05f335ef82b39d9b74520de5
Author: Philip Withnall <philip tecnocode co uk>
Date:   Sun Jun 14 11:19:51 2015 +0100

    build: Fix unit tests to use new automake parallel test harness
    
    Otherwise you get errors like the following with automake 1.14:
       /bin/bash: /bin/bash: cannot execute binary file
       Makefile:853: recipe for target 'sets.log' failed
    
    https://bugzilla.gnome.org/show_bug.cgi?id=750929

 tests/Makefile.am |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)
---
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 6c9c030..367a414 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -1,9 +1,10 @@
-TESTS_ENVIRONMENT = \
-       G_SLICE=debug-blocks \
+AM_TESTS_ENVIRONMENT = \
+       export G_SLICE=debug-blocks \
        LD_LIBRARY_PATH=$(top_builddir)/libgupnp-dlna/.libs:$(LD_LIBRARY_PATH) \
-       MEDIA_DIR="$(srcdir)/media" FILE_LIST="$(srcdir)/media/media-list.txt" ${SHELL}
+       MEDIA_DIR="$(srcdir)/media" FILE_LIST="$(srcdir)/media/media-list.txt";
 TESTS = $(check_PROGRAMS) test-discoverer.sh
 
+check_SCRIPTS = test-discoverer.sh
 check_PROGRAMS = sets
 
 sets_SOURCES = \