use cross platform path separatator in build

Author: Martijn Hoekstra

project/Build.scala

@@ -453,7 +453,7 @@ object Build {
   def findLib(attList: Seq[Attributed[File]], name: String) = attList
     .map(_.data.getAbsolutePath)
     .find(_.contains(name))
-    .toList.mkString(":")
+    .toList.mkString(java.io.File.pathSeparatorChar.toString)
 
   // Settings shared between dotty-compiler and dotty-compiler-bootstrapped
   lazy val commonDottyCompilerSettings = Seq(
@@ -682,13 +682,13 @@ object Build {
       else if (debugFromTasty) "dotty.tools.dotc.fromtasty.Debug"
       else "dotty.tools.dotc.Main"
 
-    var extraClasspath = s"$scalaLib:$dottyLib"
-    if ((decompile || printTasty) && !args.contains("-classpath")) extraClasspath += ":."
+    var extraClasspath = s"$scalaLib${java.io.File.pathSeparator}$dottyLib"
+    if ((decompile || printTasty) && !args.contains("-classpath")) extraClasspath += s"${java.io.File.pathSeparator}."
     if (args0.contains("-with-compiler")) {
       if (!isDotty.value) {
         throw new MessageOnlyException("-with-compiler can only be used with a bootstrapped compiler")
       }
-      extraClasspath += s":$dottyCompiler"
+      extraClasspath += s"${java.io.File.pathSeparator}:$dottyCompiler"
     }
 
     val fullArgs = main :: insertClasspathInArgs(args, extraClasspath)