Sync logic with ruby-builder

Author: eregon

.github/workflows/build.yml

@@ -107,12 +107,14 @@ jobs:
       if: "!startsWith(matrix.os, 'windows')"
     # NOTE: Keep the logic from here in sync with ruby-builder's buildJRubyWindows job
     # Extracting must be done in the native shell: https://github.com/MSP-Greg/ruby-setup-ruby/issues/1
-    # We need to use to use the system tar, the Git tar seems basically broken
+    # We need to use to use the system tar, the Git tar seems basically broken.
+    # And `mv dir /c/...` also removes jruby.exe, so we need to avoid that.
     - run: C:\windows\system32\tar.exe xf jruby-head.tar.gz
       if: startsWith(matrix.os, 'windows')
-    - name: Rename to jruby-head
+    - name: Check bin/ and rename to jruby-head
       shell: bash
       run: |
+        ls -l jruby-*-SNAPSHOT/bin
         mv jruby-*-SNAPSHOT jruby-head
         ls -l jruby-head/bin
     - name: Create archive