how to include library project in Jacoco coverage report?

Question

Already included with mainSrc:

root > src > main > java

Library I want to include (myLibrarySrc):

root > libraries > myLibrary > src > main > java

My attempt inside task jacocoTestReport:

def mainSrc = "$project.projectDir/src/main/java"
def myLibrarySrc = [project.file("libraries/myLibrary"), "/src/main/java"]

sourceDirectories = files([mainSrc], librarySrc)

I haven't been able to log output so I'm kind of flying blind.