[gmime] Fixed tests/Makefile.am to exit with a non-negative value

[Rico Tzschichholz <ricotz src gnome org>]

commit a1a747eba7ccde2c27f21daaa1ecffc46f18a707
Author: Jeffrey Stedfast <jestedfa microsoft com>
Date:   Sun Feb 16 09:39:58 2020 -0500

    Fixed tests/Makefile.am to exit with a non-negative value
    
    Fixes issue #82

 tests/Makefile.am | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 9a2ee8d4..8bb2d111 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -166,7 +166,7 @@ check-local: $(AUTOMATED_TESTS)
        echo "Results: $${passed} tests passed; $${failed} tests failed."; \
        if [ $${failed} -ne 0 ]; then \
                echo -e "Failed tests: $${failed_tests}"; \
-               exit -1; \
+               exit 255; \
        fi
 
 distclean-local: