Use correct classpath format on windows

Bug: b/302213336
Change-Id: I52eb610f39020778b3af11c330ffd899eb0803ea
diff --git a/d8_r8/commonBuildSrc/src/main/kotlin/DependenciesPlugin.kt b/d8_r8/commonBuildSrc/src/main/kotlin/DependenciesPlugin.kt
index 2b49397..9d58946 100644
--- a/d8_r8/commonBuildSrc/src/main/kotlin/DependenciesPlugin.kt
+++ b/d8_r8/commonBuildSrc/src/main/kotlin/DependenciesPlugin.kt
@@ -248,7 +248,7 @@
     "-Xmx8g",
     "-ea",
     "-cp",
-    "$jar:$deps",
+    getClasspath(jar, deps),
     "com.android.tools.r8.SwissArmyKnife",
     compiler) + args
 }