wrappers: Add a wrapper for running llvm binutils replacements

This saves a lot of diskspace, when symlinks are turned into full
copies of the tools on windows, as the symlinks only point to a small
wrapper instead of to the full tool.

wrappers/clang-target-wrapper.c

@@ -222,23 +222,7 @@ int _tmain(int argc, TCHAR* argv[]) {
     for (int i = 1; i < argc; i++)
         if (!_tcscmp(argv[i], _T("-v")))
             return exec_filtered(exec_argv);
-
-    int ret = _tspawnvp_escape(_P_WAIT, exec_argv[0], exec_argv);
-    if (ret == -1) {
-        _tperror(exec_argv[0]);
-        return 1;
-    }
-    return ret;
-#else
-    // On unix, exec() runs the target executable within this same process,
-    // making the return code propagate implicitly.
-    // Windows doesn't have such mechanisms, and the exec() family of functions
-    // makes the calling process exit immediately and always returning
-    // a zero return. This doesn't work for our case where we need the
-    // return code propagated.
-    _texecvp(exec_argv[0], EXECVP_CAST exec_argv);
-
-    _tperror(exec_argv[0]);
-    return 1;
 #endif
+
+    return run_final(exec_argv[0], exec_argv);
 }

wrappers/llvm-wrapper.c

@@ -0,0 +1,28 @@
+/*
+ * Copyright (c) 2018 Martin Storsjo
+ *
+ * This file is part of llvm-mingw.
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include "native-wrapper.h"
+
+int _tmain(int argc, TCHAR* argv[]) {
+    const TCHAR *dir;
+    const TCHAR *exe;
+    split_argv(argv[0], &dir, NULL, NULL, &exe);
+    TCHAR *exe_path = concat(dir, concat(_T("llvm-"), exe));
+
+    return run_final(exe_path, (const TCHAR *const *) argv);
+}

wrappers/native-wrapper.h

@@ -158,3 +158,25 @@ static void split_argv(const TCHAR *argv0, const TCHAR **dir_ptr, const TCHAR **
     if (exe_ptr)
         *exe_ptr = exe;
 }
+
+static int run_final(const TCHAR *executable, const TCHAR *const *argv) {
+#ifdef _WIN32
+    int ret = _tspawnvp_escape(_P_WAIT, executable, argv);
+    if (ret == -1) {
+        _tperror(executable);
+        return 1;
+    }
+    return ret;
+#else
+    // On unix, exec() runs the target executable within this same process,
+    // making the return code propagate implicitly.
+    // Windows doesn't have such mechanisms, and the exec() family of functions
+    // makes the calling process exit immediately and always returning
+    // a zero return. This doesn't work for our case where we need the
+    // return code propagated.
+    _texecvp(executable, EXECVP_CAST argv);
+
+    _tperror(executable);
+    return 1;
+#endif
+}