exclude clang18+debug from freestanding again

.github/generate-job-matrix.py

@@ -119,7 +119,12 @@ def main():
 
     rgen = random.Random(args.seed)
 
-    collector = CombinationCollector(full_matrix)
+    collector = CombinationCollector(
+        full_matrix,
+        hard_excludes=lambda e: (
+            e.formatting == "std::format" and not e.config.std_format_support
+        ),
+    )
     match args.preset:
         case None:
             pass
@@ -143,7 +148,11 @@ def main():
         case "clang-tidy":
             collector.all_combinations(config=configs["Clang-18 (x86-64)"])
         case "freestanding":
+            # TODO For some reason Clang-18 Debug with -ffreestanding does not pass CMakeTestCXXCompiler
             collector.all_combinations(
+                filter=lambda e: not (
+                    e.config.name.startswith("Clang-18") and e.build_type == "Debug"
+                ),
                 config=[configs[c] for c in ["GCC-14", "Clang-18 (x86-64)"]],
                 contracts="none",
                 std=23,

.github/job_matrix.py

@@ -55,8 +55,14 @@ def dataclass_to_json(obj):
 class CombinationCollector:
     """Incremental builder of MatrixElements, allowing successive selection of entries."""
 
-    def __init__(self, full_matrix: dict[str, list[typing.Any]]):
+    def __init__(
+        self,
+        full_matrix: dict[str, list[typing.Any]],
+        *,
+        hard_excludes: typing.Callable[[MatrixElement], bool] | None = None,
+    ):
         self.full_matrix = full_matrix
+        self.hard_excludes = hard_excludes
         self.combinations: set[MatrixElement] = set()
         self.per_value_counts: dict[tuple[str, typing.Any], int] = {
             (k, v): 0 for k, options in full_matrix.items() for v in options
@@ -72,7 +78,7 @@ def _make_submatrix(self, **overrides):
 
     def _add_combination(self, e: MatrixElement):
         if e in self.combinations or (
-            e.formatting == "std::format" and not e.config.std_format_support
+            self.hard_excludes is not None and self.hard_excludes(e)
         ):
             return
         self.combinations.add(e)