try to fix issue with building in windows

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1891467 13f79535-47bb-0310-9956-ffa450edef68

poi-ooxml/build.gradle

@@ -224,7 +224,7 @@ test {
         if (JavaVersion.current() != JavaVersion.VERSION_1_8) {
             jvmArgs += [
                 '--add-modules', MODULE_NAME,
-                '--module-path', '../build/dist/maven/poi-ooxml-tests:' + files(TEST_MODULE_PATH).asPath,
+                '--module-path', '../build/dist/maven/poi-ooxml-tests' + java.io.File.pathSeparator + files(TEST_MODULE_PATH).asPath,
             ]
         }
     }