Merge pull request #184 from makenowjust/refspec

Correct refspec to fetch Ruby source

Author: kateinoigakukun

lib/ruby_wasm/build_system/product/ruby_source.rb

@@ -39,10 +39,10 @@ def fetch
         system "git init", chdir: src_dir
         system "git remote add origin #{repo_url}", chdir: src_dir
         system(
-          "git fetch --depth 1 origin #{@params[:rev]}:#{@params[:rev]}",
+          "git fetch --depth 1 origin #{@params[:rev]}:origin/#{@params[:rev]}",
           chdir: src_dir
         ) or raise "failed to clone #{repo_url}"
-        system("git checkout #{@params[:rev]}", chdir: src_dir) or
+        system("git checkout origin/#{@params[:rev]}", chdir: src_dir) or
           raise "failed to checkout #{@params[:rev]}"
       when "local"
         FileUtils.mkdir_p File.dirname(src_dir)