load_path: trim entries where possible to fix Ruby crashes

Library/Homebrew/load_path.rb

@@ -4,6 +4,9 @@ require "pathname"
 
 HOMEBREW_LIBRARY_PATH = Pathname(__dir__).realpath.freeze
 
-$LOAD_PATH.push(HOMEBREW_LIBRARY_PATH.to_s) unless $LOAD_PATH.include?(HOMEBREW_LIBRARY_PATH.to_s)
+$LOAD_PATH.push HOMEBREW_LIBRARY_PATH.to_s
 
 require "vendor/bundle/bundler/setup"
+
+$LOAD_PATH.select! { |d| Pathname(d).directory? }
+$LOAD_PATH.uniq!

Library/Homebrew/test/support/helper/spec/shared_context/integration_test.rb

@@ -9,11 +9,6 @@ RSpec::Matchers.define_negated_matcher :be_a_failure, :be_a_success
 RSpec.shared_context "integration test" do
   extend RSpec::Matchers::DSL
 
-  if OS.mac? &&
-     !RUBY_BIN.to_s.match?(%r{^/(System/Library/Frameworks/Ruby\.framework/Versions/(Current|\d+\.\d+)/)usr/bin$})
-    skip "integration test requires system Ruby"
-  end
-
   matcher :be_a_success do
     match do |actual|
       status = actual.is_a?(Proc) ? actual.call : actual