Handle Ruby 3.1 eval location change

Ref: ruby/ruby#4519

On Ruby 3.1, `Backtrace::Location#absolute_path` returns `nil` if the
code was loaded with eval. That same PR made `require_relative` fallback
to `Backtrace::Location#path` in such case, so we're doing the same.

lib/bootsnap/load_path_cache/core_ext/kernel_require.rb

@@ -47,8 +47,9 @@ def require(path)
 
   alias_method(:require_relative_without_bootsnap, :require_relative)
   def require_relative(path)
+    location = caller_locations(1..1).first
     realpath = Bootsnap::LoadPathCache.realpath_cache.call(
-      caller_locations(1..1).first.absolute_path, path
+      location.absolute_path || location.path, path
     )
     require(realpath)
   end