Enable the ability to run a binary manually

[taekahn]

Hi,
I was using this, and bazel run //:whatever_binary works great, but if you try to run it manually via bazel-bin/whatever_binary.rb.sh, it will fail to find the relative path to the executable.

A simple patch will fix ithis.

index 4cd69dca..72771452 100644
--- ruby/private/binary.bzl
+++ ruby/private/binary.bzl
@@ -59,7 +59,7 @@ def generate_rb_binary_script(ctx, binary, bundler = False, args = [], env = {},
     toolchain_bindir = toolchain.bindir
 
     if binary:
-        binary_path = binary.short_path
+        binary_path = "${BUNDLE_BIN}/" + binary.basename
     else:
         binary_path = ""

I can fork and make a PR if that is desired, but its a simple change, so i decided to create it as an issue.

Thanks.

edit: Also i'm not sure if this change will actually break anything else.
Ultimately it would be nice to be able to run the command directly.

[p0deje]

@taekahn I would appreciate if you open a PR with this change so that at least Ci runs - there might be some problems on Windows

[p0deje]

So in the next version, you should be able to use binaries directly, I even dropped.rb.sh suffix so it looks like a regular binary, for example:

$ bazel build @ruby//...
$ bazel-bin/external/ruby/ruby --version
jruby 9.4.5.0 (3.1.4) 2023-11-02 1abae2700f OpenJDK 64-Bit Server VM 11.0.20+8-LTS on 11.0.20+8-LTS +jit [arm64-darwin]

# This only works for `rb_bundle_fetch()` repository rule
$ bazel build @bundle//...
$ bazel-bin/external/bundle/bin/rspec --version
RSpec 3.11
  - rspec-core 3.11.0
  - rspec-expectations 3.11.1
  - rspec-mocks 3.11.1
  - rspec-support 3.11.1

You can probably take it even further and add bundle-bin/external/ruby / bundle-bin/external/bundle/bin to the PATH.

Note that Windows is not supported at the moment.