fix windows not detecting prerelease

Author: umbynos

.github/workflows/release.yml

@@ -38,6 +38,7 @@ jobs:
           wget -q -P /tmp https://github.com/fsaintjacques/semver-tool/archive/3.1.0.zip
           unzip -p /tmp/3.1.0.zip semver-tool-3.1.0/src/semver >/tmp/semver && chmod +x /tmp/semver
           if [[ $(/tmp/semver get prerel ${GITHUB_REF/refs\/tags\//}) ]]; then echo "::set-output name=IS_PRE::true"; fi
+        shell: bash
 
       - name: Disable EOL conversions
         run: git config --global core.autocrlf false