Add script to automate removing repo symlinks

We need to use a fork of the cxx crate until something like
dtolnay#1343 can hopefully be merged
upstream but we also don't want to require Windows developers to
have to enable support for symlinks, so we'll instead copy the
syntax directory, similar to what would effectively happen when
the cxx crate is published to crates.io

copy-syntax.sh

@@ -0,0 +1,15 @@
+#!/bin/bash
+
+SYMLINKS="./gen/build/src/syntax \
+./gen/cmd/src/syntax \
+./gen/lib/src/syntax \
+./macro/src/syntax"
+
+for symlink in $SYMLINKS
+do
+    rm -fr $symlink
+    cp -av ./syntax $symlink
+    git add $symlink
+done
+
+git commit -m "Remove repo symlinks by copying ./syntax directory"