Resolve signing.secretKeyRingFile relative to root project

build.gradle

@@ -9,7 +9,7 @@ allprojects {
   project.version = '3.3.0-SNAPSHOT'
   project.ext.isSnapshot = project.version.endsWith("-SNAPSHOT")
 
-  ext."signing.secretKeyRingFile" = file("secring.gpg").absolutePath
+  ext."signing.secretKeyRingFile" = rootProject.file("secring.gpg").absolutePath
 }
 
 wrapper {