fix: skip fallback header_contents tests on clang 9

clang 9's clang_Cursor_Evaluate returns CXEval_UnExposed instead of
CXEval_Int for macro-expanded expressions loaded through a PCH, so
clang_macro_fallback produces no constants on that version. The
existing header-based fallback tests already handle this with
clang-9-specific empty expectation files; apply the same pattern to
the new inline tests by skipping when libclang 9 is detected.

Author: zRedShift

bindgen-tests/tests/tests.rs

@@ -617,8 +617,18 @@ fn test_macro_fallback_non_system_dir() {
     }
 }
 
+/// clang 9's `clang_Cursor_Evaluate` returns `CXEval_UnExposed` instead
+/// of `CXEval_Int` for macro-expanded expressions through PCH, so
+/// `clang_macro_fallback` produces no constants on that version.
+fn clang_fallback_works() -> bool {
+    !matches!(clang_version().parsed, Some((9, _)))
+}
+
 #[test]
 fn test_macro_fallback_header_contents() {
+    if !clang_fallback_works() {
+        return;
+    }
     let tmpdir = tempfile::tempdir().unwrap();
     let actual = builder()
         .disable_header_comment()
@@ -647,6 +657,9 @@ fn test_macro_fallback_header_contents() {
 
 #[test]
 fn test_macro_fallback_multiple_header_contents() {
+    if !clang_fallback_works() {
+        return;
+    }
     let tmpdir = tempfile::tempdir().unwrap();
     let actual = builder()
         .disable_header_comment()
@@ -675,6 +688,9 @@ fn test_macro_fallback_multiple_header_contents() {
 
 #[test]
 fn test_macro_fallback_mixed_header_and_header_contents() {
+    if !clang_fallback_works() {
+        return;
+    }
     let tmpdir = tempfile::tempdir().unwrap();
     let actual = builder()
         .disable_header_comment()
@@ -709,6 +725,9 @@ fn test_macro_fallback_mixed_header_and_header_contents() {
 
 #[test]
 fn test_macro_fallback_header_contents_duplicate_basename() {
+    if !clang_fallback_works() {
+        return;
+    }
     let tmpdir = tempfile::tempdir().unwrap();
     let actual = builder()
         .disable_header_comment()
@@ -743,6 +762,9 @@ fn test_macro_fallback_header_contents_duplicate_basename() {
 
 #[test]
 fn test_macro_fallback_header_contents_absolute_name() {
+    if !clang_fallback_works() {
+        return;
+    }
     // Absolute names must not escape the build dir — they should be
     // materialized safely under it, and the original file must not be
     // clobbered or deleted.
@@ -788,6 +810,9 @@ fn test_macro_fallback_header_contents_absolute_name() {
 
 #[test]
 fn test_macro_fallback_header_contents_parent_dir_escape() {
+    if !clang_fallback_works() {
+        return;
+    }
     // Names with ".." must not escape the build dir or delete files
     // outside it during FallbackTranslationUnit cleanup.
     let tmpdir = tempfile::tempdir().unwrap();
@@ -826,6 +851,9 @@ fn test_macro_fallback_header_contents_parent_dir_escape() {
 
 #[test]
 fn test_macro_fallback_cross_target() {
+    if !clang_fallback_works() {
+        return;
+    }
     // Subprocess-style test: setting TARGET as an env var in a parallel
     // test is not robust, so we re-invoke the test binary as a child
     // process with TARGET set to a non-host triple. The child runs the