Only make the prefixless widl symlink after compiling widl

When building in msys2, symlinks are plain copies, and one can't
make the symlink in advance.

install-wrappers.sh

@@ -78,7 +78,7 @@ if [ -n "$EXEEXT" ]; then
     if [ -z "$HOST" ]; then
         HOST=$(./clang-$CLANG_MAJOR -dumpmachine | sed 's/-.*//')-w64-mingw32
     fi
-    for exec in clang clang++ gcc g++ cc c99 c11 c++ ar ranlib nm objcopy strings strip widl windres; do
+    for exec in clang clang++ gcc g++ cc c99 c11 c++ ar ranlib nm objcopy strings strip windres; do
         ln -sf $HOST-$exec$EXEEXT $exec$EXEEXT
     done
     for exec in ld objdump dlltool; do