TESTS_ENVIRONMENT is deprecated and should be reserved to the user to
override the test environment
<ext>_LOG_COMPILER is meant to contain the program that runs the test
with <ext> extension
AM_TESTS_ENVIRONMENT is meant to set the environment for the tests
https://bugs.freedesktop.org/show_bug.cgi?id=60192
Signed-off-by: Quentin Glidic <sardemff7+git@sardemff7.net>