fix quoting in pipeline groovy

.jenkins_msys2

@@ -44,7 +44,13 @@ pipeline {
         }
         stage('msys2_x86_64_shared') {
           steps {
-            script { retryWithBackoff(2, 5) { bat 'scripts\\test_msys2.cmd shared "" x86_64' } }
+            script { 
+              retryWithBackoff(2, 5) {
+                bat '''
+                  scripts\\test_msys2.cmd shared "" x86_64
+                '''
+              } 
+            }
           }
         }
         stage('msys2_x86_64_shared_crypto') {