ci: skip CVS and P4 tests in leaks job, too

Looking at the CI logs, the p4 and cvs tests account for another 24
minutes of test time and they offer minimal value for quite a
similar reason as the previous step.

Let's introduce and use a mechanism to skip these tests to save
some resources.

Suggested-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

ci/lib.sh

@@ -356,7 +356,9 @@ linux-musl-meson)
 	;;
 linux-leaks|linux-reftable-leaks)
 	export SANITIZE=leak
+	export NO_CVS_TESTS=LetsSaveSomeTime
 	export NO_SVN_TESTS=LetsSaveSomeTime
+	export NO_P4_TESTS=LetsSaveSomeTime
 	;;
 linux-asan-ubsan)
 	export SANITIZE=address,undefined

t/lib-cvs.sh

@@ -2,6 +2,12 @@
 
 . ./test-lib.sh
 
+if test -n "$NO_CVS_TESTS"
+then
+	skip_all='skipping git cvs tests, NO_CVS_TESTS defined'
+	test_done
+fi
+
 unset CVS_SERVER
 
 if ! type cvs >/dev/null 2>&1

t/lib-git-p4.sh

@@ -16,6 +16,11 @@ P4D_TIMEOUT=300
 
 . ./test-lib.sh
 
+if test -n "$NO_P4_TESTS"
+then
+	skip_all='skipping git p4 tests, NO_P4_TESTS defined'
+	test_done
+fi
 if ! test_have_prereq PYTHON
 then
 	skip_all='skipping git p4 tests; python not available'