mtest2make.py: teach suite name that are just "PROJECT"

A subproject test may be simply in the "PROJECT" suite (such as
"qemu-common" with the following patches)

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20230302131848.1527460-2-marcandre.lureau@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

scripts/mtest2make.py

@@ -51,10 +51,11 @@ def process_tests(test, targets, suites):
 
     test_suites = test['suite'] or ['default']
     for s in test_suites:
-        # The suite name in the introspection info is "PROJECT:SUITE"
-        s = s.split(':')[1]
-        if s == 'slow' or s == 'thorough':
-            continue
+        # The suite name in the introspection info is "PROJECT" or "PROJECT:SUITE"
+        if ':' in s:
+            s = s.split(':')[1]
+            if s == 'slow' or s == 'thorough':
+                continue
         if s.endswith('-slow'):
             s = s[:-5]
             suites[s].speeds.append('slow')