core: build: Fix windows build

Core module build was failing on windows as there were some errors
in ballerian build script for windows.

components/micro-gateway-core/scripts/ballerina-build.bat

@@ -17,16 +17,16 @@ REM  limitations under the License.
 SET BALLERINA_HOME=%1
 SET MAVEN_PROJECT_ROOT=%2
 SET BAL_EXEC="%BALLERINA_HOME%\bin\ballerina"
-SET GATEWAY_PROJECT="%MAVEN_PROJECT_ROOT%\src\main\ballerina\"
+SET GATEWAY_PROJECT="%MAVEN_PROJECT_ROOT%\src\main\ballerina"
 
 REM Quietly delete the directory structure in %GATEWAY_PROJECT%\target
 RMDIR /S /Q %GATEWAY_PROJECT%\target
 
 PUSHD %GATEWAY_PROJECT%
-    %BAL_EXEC% build -c --experimental gateway
+CALL %BAL_EXEC% build -c --experimental gateway
 POPD
 
-cp -r %GATEWAY_PROJECT%\target\caches\bir_cache %MAVEN_PROJECT_ROOT%\target
-cp -r %GATEWAY_PROJECT%\target\caches\jar_cache %MAVEN_PROJECT_ROOT%\target
-cp -r %GATEWAY_PROJECT%\target\balo %MAVEN_PROJECT_ROOT%\target
+xcopy /Y /I /E %GATEWAY_PROJECT%\target\caches\bir_cache %MAVEN_PROJECT_ROOT%\target\bir_cache
+xcopy /Y /I /E %GATEWAY_PROJECT%\target\caches\jar_cache %MAVEN_PROJECT_ROOT%\target\jar_cache
+xcopy /Y /I /E %GATEWAY_PROJECT%\target\balo %MAVEN_PROJECT_ROOT%\target\balo