Allow building libsignal from source.

Co-authored-by: Jordan Rose <jrose@signal.org>

gradle.properties

@@ -4,3 +4,7 @@ android.experimental.androidTest.numManagedDeviceShards=4
 android.defaults.buildfeatures.buildconfig=true
 android.nonTransitiveRClass=false
 android.nonFinalResIds=false
+
+# Uncomment these to build libsignal from source.
+# libsignalClientPath=../libsignal
+# org.gradle.dependency.verification=lenient

settings.gradle.kts

@@ -29,6 +29,18 @@ dependencyResolutionManagement {
   }
 }
 
+// To build libsignal from source, set the libsignalClientPath property in gradle.properties.
+val libsignalClientPath = if (extra.has("libsignalClientPath")) extra.get("libsignalClientPath") else null;
+if (libsignalClientPath is String) {
+  includeBuild(rootDir.resolve(libsignalClientPath + "/java")) {
+    name = "libsignal-client"
+    dependencySubstitution {
+      substitute(module("org.signal:libsignal-client")).using(project(":client"))
+      substitute(module("org.signal:libsignal-android")).using(project(":android"))
+    }
+  }
+}
+
 include(":app")
 include(":libsignal-service")
 include(":lintchecks")