Fix: actions/build_release> use bash to run script on all OS

Without specifying this, Windows runner will use PowerShell
instead of bash

.github/workflows/build_release.yaml

@@ -21,6 +21,7 @@ jobs:
           enable-stack: true
 
       - name: build executable
+        shell: bash
         run: |
           stack build
           find .stack-work/install -name oschark -exec mv {} . \;