compileReleaseJavaWithJavac - is not incremental (e.g. outputs have changed, no previous execution, etc.)

Help/Discuss
1

I have below project structure

Project A root contains
— Library Project 1
— Library Project 2
— LIbrary Project 3

Project B (JAVA) added as submodule to Project A

Library Project 2 needs some jar files and also .so files from Project B . So i wrote two task .

One is to build the Project B and another is copy neccessary files from Project B to Library Project 2 in Project A

My Library Project 2 build.gradle

task buildProjectB (type: Exec) {
commandLine ‘./build.sh’ //It will build project B and generated jars and .so files
}

task copyLibraries (type: Copy, dependsOn: buildProjectB) {

from "location of jar 1 in Project B"
into "libs"

from "location of jar 2  in Project B"
into "libs"

from "location .so files  in Project B"
into "libs"

}

preBuild.dependsOn copyLibraries

All libraries copied in to libs folder successfully , but (./gradlew clean build) build failing
compileReleaseJavWithJavac - is not incremental (e.g. outputs have changed, no previous execution, etc.).

error: cannot find symbol which is present inside the libraries (libs) but not exported

Kindly help me to resolve this issue .