build: Use AM_TESTS_ENVIRONMENT rather than TESTS_ENVIRONMENT

TESTS_ENVIRONMENT is reserved for the user to be able to set when
running the tests. AM_TESTS_ENVIRONMENT is for the tests’ Makefile to
set itself.

https://www.gnu.org/software/automake/manual/html_node/Scripts_002dbased-Testsuites.html

Signed-off-by: Philip Withnall <withnall@endlessm.com>

https://bugzilla.gnome.org/show_bug.cgi?id=782996

glib-tap.mk

@@ -1,6 +1,6 @@
 # GLIB - Library of useful C routines
 
-TESTS_ENVIRONMENT= \
+AM_TESTS_ENVIRONMENT= \
 	G_TEST_SRCDIR="$(abs_srcdir)" 		\
 	G_TEST_BUILDDIR="$(abs_builddir)" 	\
 	G_DEBUG=gc-friendly 			\

tests/Makefile.am

@@ -79,7 +79,7 @@ dist_test_data = \
 check_PROGRAMS += $(installed_test_programs) $(installed_test_extra_programs)
 check_SCRIPTS += $(installed_test_scripts)
 TESTS += $(installed_test_programs) $(dist_uninstalled_test_extra_scripts)
-TESTS_ENVIRONMENT = \
+AM_TESTS_ENVIRONMENT = \
 	G_TEST_SRCDIR=$(abs_srcdir)				\
 	G_TEST_BUILDDIR=$(abs_builddir)				\
 	LIBCHARSET_ALIAS_DIR=$(top_builddir)/glib/libcharset	\

tests/gobject/Makefile.am

@@ -34,7 +34,7 @@ noinst_PROGRAMS += \
 # This will cause them to be built even if installed tests are disabled.
 check_PROGRAMS += $(installed_test_programs) $(installed_test_extra_programs)
 TESTS += $(installed_test_programs)
-TESTS_ENVIRONMENT = \
+AM_TESTS_ENVIRONMENT = \
 	LIBCHARSET_ALIAS_DIR=$(top_builddir)/glib/libcharset    \
 	MALLOC_CHECK_=2                                         \
 	MALLOC_PERTURB_=$$(($${RANDOM:-256} % 256))

tests/refcount/Makefile.am

@@ -20,7 +20,7 @@ TESTS += \
 	signal4					\
 	$(NULL)
 
-TESTS_ENVIRONMENT = srcdir=$(srcdir) \
+AM_TESTS_ENVIRONMENT = srcdir=$(srcdir) \
 	LIBCHARSET_ALIAS_DIR=$(top_builddir)/glib/libcharset
 
 signal1_SOURCES = signals.c