wrappers: Only escape arguments that need escaping

This avoids inflating the total size of the command line too much.

If the input command line is near the max size of a command line
(32767 characters), it may grow past that limit when adding the
arguments injected by the wrapper. If we excessively quote all
arguments that don't need to be quoted, we can more easily run
into this situation.

Thus, by avoiding excessive quoting, we reduce the risk for this
issue to happen.

This avoids the issue reported at
https://github.com/mstorsjo/llvm-mingw/issues/296.

wrappers/native-wrapper.h

@@ -58,7 +58,11 @@ typedef char TCHAR;
 #endif
 
 #ifdef _WIN32
-static inline TCHAR *escape(const TCHAR *str) {
+static inline const TCHAR *escape(const TCHAR *str) {
+    // If we don't need to escape anything, just return the input string
+    // as is.
+    if (!_tcschr(str, ' ') && !_tcschr(str, '"'))
+        return str;
     TCHAR *out = malloc((_tcslen(str) * 2 + 3) * sizeof(*out));
     TCHAR *ptr = out;
     int i;