WORKSPACE rules can break on case-insensitive file systems (e.g. OSX)

[GregBowyer]

Description of the problem / feature request / question:

This is related somewhat to #552

Lets say you have a WORKSPACE rule like so

new_git_repository(
    name = 'ck',
    remote = 'https://github.com/concurrencykit/ck.git',
    tag = '0.5.2',
    build_file = 'build_tools/externals/libck.BUILD',
)

And lets say that directory expands like so

gregbowyer@USSFRGBO-ML ~/work$ ls /private/var/tmp/_bazel_gregbowyer/ed2084cb983d1d34833966860868e551/external/ck
LICENSE  Makefile.in  README  WORKSPACE  build  configure  doc  include  regressions  src  tools
gregbowyer@USSFRGBO-ML ~/work$

That leads to the irritating situation where we try to copy libck.BUILD into that directory as BUILD.
This is different from #552 in that in WORKSPACE rules we dont seem to have the ability to state it should become BUILD.bzl. Maybe just defaulting to BUILD.bzl will work as a solution?

Environment info

• Operating System: OSX (but I figure anything with a case-insensitive filesystem)
• Bazel version (output of bazel info release):

gregbowyer@USSFRGBO-ML ~/work/pers $ bazel version
Build label: 0.4.3-homebrew
Build target: bazel-out/local-opt/bin/src/main/java/com/google/devtools/build/lib/bazel/BazelServer_deploy.jar
Build time: Thu Dec 22 15:20:22 2016 (1482420022)
Build timestamp: 1482420022
Build timestamp as int: 1482420022

[katre]

What version of Bazel are you using? I recently committed b9c65d1 (after initially committing it, then reverting it), which does exactly this: external repositories will use BUILD.bazel instead of BUILD to fix this issue.

Can you try building Bazel from head and seeing if that has the same issue? This is pretty much a duplicate of #2226.

[GregBowyer]

Yes that fixed it