Getting error while performing custom build for OpenCV 4.9.0 for android

[100%] Linking CXX shared library …....\jni\arm64-v8a\
[100%] Built target opencv_java
[100%] Copy Java(Android SDK) source files
[100%] Built target opencv_java_android_source_copy
[100%] Building OpenCV Android library project
‘.\gradlew’ is not recognized as an internal or external command,
operable program or batch file.
modules\java\android_sdk\CMakeFiles\opencv_java_android.dir\build.make:72: recipe for target ‘/opencv/build/outputs/aar/opencv-release.aar’ failed
mingw32-make[2]: *** [/opencv/build/outputs/aar/opencv-release.aar] Error 1
CMakeFiles\Makefile2:2618: recipe for target ‘modules/java/android_sdk/CMakeFiles/opencv_java_android.dir/all’ failed
mingw32-make[1]: *** [modules/java/android_sdk/CMakeFiles/opencv_java_android.dir/all] Error 2
Makefile:164: recipe for target ‘all’ failed
mingw32-make: *** [all] Error 2

Getting following error while building OpenCV for android arm64-v8a. Gradle is already present and I have set the environment variables for the same. Any help would be greatly appreciated as I tried to take help from multiple blogs but couldnt resolve the error.