add config to explicitely test rustc with autodiff/enzyme disabled

Author: ZuseZ4

src/tools/compiletest/src/command-list.rs

@@ -49,6 +49,7 @@ const KNOWN_DIRECTIVE_NAMES: &[&str] = &[
     "ignore-eabi",
     "ignore-emscripten",
     "ignore-endian-big",
+    "ignore-enzyme",
     "ignore-freebsd",
     "ignore-fuchsia",
     "ignore-gdb",

src/tools/compiletest/src/header/cfg.rs

@@ -166,6 +166,12 @@ pub(super) fn parse_cfg_name_directive<'a>(
         message: "when the target vendor is Apple"
     }
 
+    condition! {
+        name: "enzyme",
+        condition: config.has_enzyme,
+        message: "when rustc is built with LLVM Enzyme"
+    }
+
     // Technically the locally built compiler uses the "dev" channel rather than the "nightly"
     // channel, even though most people don't know or won't care about it. To avoid confusion, we
     // treat the "dev" channel as the "nightly" channel when processing the directive.