Use correct file path separator.

--
MOS_MIGRATED_REVID=113349046
diff --git a/src/java_tools/buildjar/java/com/google/devtools/build/buildjar/CommonJavaLibraryProcessor.java b/src/java_tools/buildjar/java/com/google/devtools/build/buildjar/CommonJavaLibraryProcessor.java
index a3e3538..ee5c727 100644
--- a/src/java_tools/buildjar/java/com/google/devtools/build/buildjar/CommonJavaLibraryProcessor.java
+++ b/src/java_tools/buildjar/java/com/google/devtools/build/buildjar/CommonJavaLibraryProcessor.java
@@ -14,6 +14,7 @@
 
 package com.google.devtools.build.buildjar;
 
+import java.io.File;
 import java.util.ArrayList;
 import java.util.List;
 
@@ -44,7 +45,7 @@
     // Add an empty source path to prevent javac from sucking in source files
     // from .jar files on the classpath.
     args.add("-sourcepath");
-    args.add(":");
+    args.add(File.pathSeparator);
 
     if (build.getExtdir() != null) {
       args.add("-extdirs");
diff --git a/src/java_tools/buildjar/java/com/google/devtools/build/buildjar/javac/plugins/dependency/DependencyModule.java b/src/java_tools/buildjar/java/com/google/devtools/build/buildjar/javac/plugins/dependency/DependencyModule.java
index aed158e..b3350d9 100644
--- a/src/java_tools/buildjar/java/com/google/devtools/build/buildjar/javac/plugins/dependency/DependencyModule.java
+++ b/src/java_tools/buildjar/java/com/google/devtools/build/buildjar/javac/plugins/dependency/DependencyModule.java
@@ -25,6 +25,7 @@
 import java.io.BufferedInputStream;
 import java.io.BufferedOutputStream;
 import java.io.BufferedWriter;
+import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileOutputStream;
 import java.io.FileWriter;
@@ -267,7 +268,7 @@
   }
 
   private static final Splitter CLASSPATH_SPLITTER = Splitter.on(':');
-  private static final Joiner CLASSPATH_JOINER = Joiner.on(':');
+  private static final Joiner CLASSPATH_JOINER = Joiner.on(File.pathSeparator);
 
   /**
    * Computes a reduced compile-time classpath from the union of direct dependencies and their