use File.pathSeparator for classpath in genDocs

- uses File.pathSeparator instead of hard-coded path separator `:`
  in genDocs => this way Windows user can run the command as well

Author: robstoll

project/Build.scala

@@ -364,9 +364,10 @@ object Build {
       val majorVersion = baseVersion.take(baseVersion.lastIndexOf('.'))
       IO.write(file("./docs/_site/versions/latest-nightly-base"), majorVersion)
 
+      val separator = File.pathSeparator
       val dottyLib = (packageAll in `dotty-compiler`).value("dotty-library")
       val dottyInterfaces = (packageAll in `dotty-compiler`).value("dotty-interfaces")
-      val otherDeps = (dependencyClasspath in Compile).value.map(_.data).mkString(":")
+      val otherDeps = (dependencyClasspath in Compile).value.map(_.data).mkString(separator)
       val sources =
         (unmanagedSources in (Compile, compile)).value ++
           (unmanagedSources in (`dotty-compiler`, Compile)).value
@@ -375,7 +376,7 @@ object Build {
         "-project", "Dotty",
         "-project-version", dottyVersion,
         "-project-url", dottyGithubUrl,
-        "-classpath", s"$dottyLib:$dottyInterfaces:$otherDeps"
+        "-classpath", dottyLib + separator + dottyInterfaces + separator + otherDeps
       )
       (runMain in Compile).toTask(
         s""" dotty.tools.dottydoc.Main ${args.mkString(" ")} ${sources.mkString(" ")}"""