Error out early if trying to compile ada

If we try to do that, clang would end up calling <triplet>-gcc with the
same arguments. In our setup, this recursively ends up calling clang again,
ending up with infinite recursion.

wrappers/clang-target-wrapper.c

@@ -142,6 +142,16 @@ int _tmain(int argc, TCHAR* argv[]) {
     if (dash)
         *dash = '\0';
 
+    // Check if trying to compile Ada; if we try to do this, invoking clang
+    // would end up invoking <triplet>-gcc with the same arguments, which ends
+    // up in an infinite recursion.
+    for (int i = 1; i < argc - 1; i++) {
+        if (!_tcscmp(argv[i], _T("-x")) && !_tcscmp(argv[i + 1], _T("ada"))) {
+            fprintf(stderr, "Ada is not supported\n");
+            return 1;
+        }
+    }
+
     int max_arg = argc + 20;
     const TCHAR **exec_argv = malloc(max_arg * sizeof(*exec_argv));
     int arg = 0;

wrappers/clang-target-wrapper.sh

@@ -9,6 +9,18 @@ if [ "$TARGET" = "$BASENAME" ]; then
 fi
 ARCH="${TARGET%%-*}"
 
+# Check if trying to compile Ada; if we try to do this, invoking clang
+# would end up invoking <triplet>-gcc with the same arguments, which ends
+# up in an infinite recursion.
+case "$*" in
+*-x\ ada*)
+    echo "Ada is not supported" >&2
+    exit 1
+    ;;
+*)
+    ;;
+esac
+
 # Allow setting e.g. CCACHE=1 to wrap all building in ccache.
 if [ -n "$CCACHE" ]; then
     CCACHE=ccache