'make test': show failing test cases when cmake does

When building with make, `make test` runs `run-test-suites.pl` which has a
verbose mode that reports the failing test cases, but it didn't provide a
way to enable this verbose mode. With the present commit, you can run `make
test TEST_FLAGS=-v` to use verbose mode.

Base the default for verbose mode on the same environment variable that
`make test` uses when building with CMake: default off, but enabled if
`CTEST_OUTPUT_ON_FAILURE` is true. In particular, verbose mode will now be
on when building from `all.sh`.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/tests/scripts/all.sh b/tests/scripts/all.sh
index f7e5a73..4005e16 100755
--- a/tests/scripts/all.sh
+++ b/tests/scripts/all.sh
@@ -186,7 +186,7 @@
         export MAKEFLAGS="-j"
     fi
 
-    # Include more verbose output for failing tests run by CMake
+    # Include more verbose output for failing tests run by CMake or make
     export CTEST_OUTPUT_ON_FAILURE=1
 
     # CFLAGS and LDFLAGS for Asan builds that don't use CMake