Fix creating r8lib and getting version for Windows

Change-Id: If8989d34b4b7e02144065991d78021b318de42ec
diff --git a/tools/create_r8lib.py b/tools/create_r8lib.py
index b0cd026..329ae8e 100755
--- a/tools/create_r8lib.py
+++ b/tools/create_r8lib.py
@@ -48,11 +48,12 @@
     fd.close()
     cmd = [jdk.GetJavacExecutable(), '-cp', r8jar, name]
     print(' '.join(cmd))
+    cp_separator = ';' if utils.IsWindows() else ':'
     subprocess.check_call(cmd)
     output = subprocess.check_output([
       jdk.GetJavaExecutable(),
       '-cp',
-      ':'.join([r8jar, os.path.dirname(name)]),
+      cp_separator.join([r8jar, os.path.dirname(name)]),
       'VersionExtractor'
     ]).decode('UTF-8').strip()
     if output == 'main':