tests: avoid unexpected failure when cmake is not installed

This test case checks stdout and demands a `dependency()` lookup fail.
The resulting error message can be different depending on whether cmake
is installed, or not. For cmake-specific tests we would simply skip the
test if cmake is not installed, but here we can just fine-tune the
pattern matching we use to determine if the test failed "correctly".

Fixes #11320

test cases/failing/111 empty fallback/test.json

@@ -1,7 +1,8 @@
 {
     "stdout": [
         {
-            "line": "test cases/failing/111 empty fallback/meson.build:6:0: ERROR: Dependency \"foo\" not found, tried pkgconfig and cmake"
+            "match": "re",
+            "line": "test cases/failing/111 empty fallback/meson.build:6:0: ERROR: Dependency \"foo\" not found.*"
         }
     ]
 }