tests/run-make/print-cfg: add Android target_env case

Android targets must not inherit `target_env="gnu"` from the Linux GNU
base. Cover this in the existing print-cfg run-make test so a future
target-spec refactor cannot silently re-introduce it.

Author: Vastargazing

tests/run-make/print-cfg/rmake.rs

@@ -48,6 +48,12 @@ fn main() {
         includes: &["unix", "target_abi=\"eabihf\""],
         disallow: &["windows"],
     });
+    // Regression test for #90834: Android must not have `target_env="gnu"`.
+    check(PrintCfg {
+        target: "i686-linux-android",
+        includes: &["unix", "target_os=\"android\""],
+        disallow: &["windows", "target_env=\"gnu\""],
+    });
 }
 
 fn check(PrintCfg { target, includes, disallow }: PrintCfg) {