Add script to fix shebangs when using --enable-load-relative

* See ruby/setup-ruby#98 (comment)

Author: eregon

.github/workflows/build.yml

@@ -44,6 +44,8 @@ jobs:
       run: ruby-install --prefix ~/build_prefix/${{ matrix.ruby }} --no-install-deps -j4 ${{ matrix.ruby }} -- --enable-shared --enable-rpath --enable-load-relative --disable-install-doc
       env:
         CPPFLAGS: "-DENABLE_PATH_CHECK=0" # https://github.com/actions/virtual-environments/issues/267
+    - name: Fix load-relative shebangs
+      run: ~/build_prefix/${{ matrix.ruby }}/bin/ruby --disable-gems fix-load-relative-shebangs.rb
     - name: Create archive
       run: tar czf ${{ matrix.ruby }}-${{ matrix.os }}.tar.gz -C ~/build_prefix ${{ matrix.ruby }}
     - name: Install Bundler if needed

fix-load-relative-shebangs.rb

@@ -0,0 +1,21 @@
+require 'rbconfig'
+
+bindir = RbConfig::CONFIG["bindir"]
+
+FIRST_LINE = "#!/bin/sh\n"
+RUBY_SHEBANG = %r{^#!/usr/bin/env ruby$}
+
+Dir.glob("#{bindir}/*") do |file|
+  if File.binread(file, FIRST_LINE.bytesize) == FIRST_LINE
+    puts "Found load-relative prolog in #{file}, removing it"
+    contents = File.binread(file)
+    puts "Before:\n#{contents}\n===" if $VERBOSE
+
+    index = contents =~ RUBY_SHEBANG
+    raise "Could not find ruby shebang in:\n#{contents}" unless index
+    contents = contents[index..-1]
+
+    puts "After:\n#{contents}\n===" if $VERBOSE
+    File.binwrite(file, contents)
+  end
+end