Read zeros from a file in gvl_release_acquire on Windows

Windows has no /dev/zero. The benchmark is about GVL handoffs rather than I/O, so a regular file of the same zeros is enough, and it is kept in the ignored data/ directory rather than left in a temporary directory.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: hsbt

benchmarks/gvl_release_acquire/benchmark.rb

@@ -1,8 +1,20 @@
 require_relative "../../harness/loader"
 
+# Windows has no /dev/zero, so read the same zeros from a regular file kept in data/.
+ZERO_PATH = if File.exist?("/dev/zero")
+  "/dev/zero"
+else
+  File.join(__dir__, "data", "zero").tap do |path|
+    unless File.size?(path) == 1_000_000
+      Dir.mkdir(File.dirname(path)) unless Dir.exist?(File.dirname(path))
+      File.binwrite(path, "\0" * 1_000_000)
+    end
+  end
+end.freeze
+
 run_benchmark(5) do |num_rs, ractor_args|
   output = File.open(File::NULL, "wb")
-  input = File.open("/dev/zero", "rb")
+  input = File.open(ZERO_PATH, "rb")
   100_000.times do
     output.write(input.read(10))
   end