C++: Add heuristics for meson configuration files

cpp/ql/lib/semmle/code/cpp/ConfigurationTestFile.qll

@@ -26,3 +26,19 @@ class CmakeTryCompileFile extends ConfigurationTestFile {
     )
   }
 }
+
+/**
+ * A file created by Meson to test the system configuration.
+ */
+class MesonPrivateTestFile extends ConfigurationTestFile {
+  MesonPrivateTestFile() {
+    this.getBaseName() = "testfile.c" and
+    exists(Folder folder, Folder parent |
+      folder = this.getParentContainer() and
+      parent = folder.getParentContainer()
+    |
+      folder.getBaseName().matches("tmp%") and
+      parent.getBaseName() = "meson-private"
+    )
+  }
+}

cpp/ql/test/query-tests/Likely Bugs/Likely Typos/ExprHasNoEffect/meson-private/tmp_abc/ExprHasNoEffect.expected

@@ -1 +0,0 @@
-| testfile.c:6:3:6:8 | call to strlen | This expression has no effect (because $@ has no external side effects). | testfile.c:3:8:3:13 | strlen | strlen |