Fixes resource_strip_prefix on Windows

[majcherm-da]

This introduces a build/test case which fails on Windows (with resource_strip_prefix used leaving / as first char) with:

PS C:\Users\...\rules_scala> bazel build //test/resource_strip_prefix/...
INFO: Analysed target //test/resource_strip_prefix:test-lib (1 packages loaded, 3 targets configured).
INFO: Found 1 target...
ERROR: C:/users/.../rules_scala/test/resource_strip_prefix/BUILD:3:1: scala //test/resource_strip_prefix:test-lib failed (Exit 1)
java.nio.file.AccessDeniedException: test\resource_strip_prefix\src\test\resources\resource.txt -> \resource.txt
        at sun.nio.fs.WindowsException.translateToIOException(WindowsException.java:83)
        at sun.nio.fs.WindowsException.rethrowAsIOException(WindowsException.java:97)
        at sun.nio.fs.WindowsFileCopy.copy(WindowsFileCopy.java:205)
        at sun.nio.fs.WindowsFileSystemProvider.copy(WindowsFileSystemProvider.java:278)
        at java.nio.file.Files.copy(Files.java:1274)
        at io.bazel.rulesscala.scalac.ScalacProcessor.copyResources(ScalacProcessor.java:309)
        at io.bazel.rulesscala.scalac.ScalacProcessor.processRequest(ScalacProcessor.java:73)
        at io.bazel.rulesscala.worker.GenericWorker.run(GenericWorker.java:114)
        at io.bazel.rulesscala.scalac.ScalaCInvoker.main(ScalaCInvoker.java:41)
Target //test/resource_strip_prefix:test-lib failed to build
Use --verbose_failures to see the command lines of failed build steps.
INFO: Elapsed time: 4.016s, Critical Path: 2.98s
INFO: 0 processes.
FAILED: Build did NOT complete successfully

and fixes it in ScalacProcessor.java

[johnynek]

The windows test failed with an error that the worker sent an unparseable result. I restarted it, but it is a bit concerning. I don't recall seeing that in osx/linux.

This would happen if there is a println somewhere since the workers operate with stdin/stdout.

[johnynek]

windows build failed again. Can you take a look and diagnose?

[johnynek]

do you want to merge master and try again?

[ittaiz]

@majcherm-da do you think you'll have capacity for this?

[ittaiz]

@majcherm-da is this still relevant?
@d-haxton @simuons maybe one of you can say after the changes you did in that area?

[liucijus]

closing as stale, feel free to reopen