Fix build.gradle with windows

build.gradle

@@ -17,6 +17,8 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
+import org.apache.tools.ant.taskdefs.condition.Os
+
 plugins {
     // Adding the base plugin fixes the following gradle warnings in IntelliJ:
     //
@@ -40,6 +42,12 @@ ext {
     uberJarName = "${artifact}-all.jar"
     jarName = "${artifact}.jar"
     libs = "${buildDir}/libs"
+
+    if (Os.isFamily(Os.FAMILY_WINDOWS)) {
+        operatingSystem = "windows"
+    } else {
+        operatingSystem = "unix"
+    }
 }
 
 compileJava.options.encoding = 'UTF-8'
@@ -105,7 +113,12 @@ if (project.hasProperty("hostname")) {
  * @return the trimmed result from stdout, stderr and the exit value
  */
 def shell(String command) {
-    def proc = ['bash', '-c', command].execute()
+    def proc
+    if (operatingSystem == "unix") {
+        proc = ['bash', '-c', command].execute()
+    } else {
+        proc = ["cmd", "/c", command].execute()
+    }
     def out = new StringBuilder()
     def err = new StringBuilder()
     proc.waitForProcessOutput(out, err)