Avoid space-containing absolute path in RUBYOPT

[hsbt]

Bundler::SharedHelpers#set_rubyopt injects -r<absolute path to bundler/setup> into RUBYOPT. Ruby splits RUBYOPT on whitespace with no quoting mechanism, so when bundler lives under an install prefix containing a space (for example C:\Program Files), the path tears apart and every child ruby spawned under bundle exec dies at boot with invalid switch in RUBYOPT: -i.

The absolute path was introduced in a5da088 so that child processes never leak to a different bundler copy. That property is kept for all currently working setups: the absolute form is still used whenever the path has no whitespace. Only in the space-containing case, which today fails unconditionally, does set_rubyopt fall back to requiring bundler/setup by feature name. set_rubylib already puts bundler's lib directory first on the child's load path via RUBYLIB (which is PATH_SEPARATOR-separated and therefore safe with spaces), so the child still resolves the same bundler copy. When bundler is the default gem in rubylibdir, RUBYLIB is not modified and the feature name resolves through the same ruby's default load path, again the same copy. The BUNDLER_SETUP variable is unaffected since it is consumed as a plain require argument in lib/rubygems.rb where spaces are harmless.

Verified on Windows with a mswin Ruby 4.0.5 and the patched bundler copied under V:\tmp\ruby with space\patched lib\:

bundler dir = "V:/tmp/ruby with space/patched lib/bundler"
RUBYOPT = "-rbundler/setup"
RUBYLIB = "V:/tmp/ruby with space/patched lib"
child: child ok, Bundler loaded from V:/tmp/ruby with space/patched lib/bundler/shared_helpers.rb
OK site5: child ruby boots and loads the intended bundler copy
control: old-style RUBYOPT child => exit 1, ruby.exe: invalid switch in RUBYOPT: -i (RuntimeError)

Related to #9695, which fixes the argv quoting half of the same space-path breakage.

🤖 Generated with Claude Code

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