Configure buildSrc to be multi-module. (#2658)

* Configure buildSrc to be multi-module.
* Declare canonicalizer plugin's descriptor via build.gradle.

buildSrc/build.gradle

@@ -6,11 +6,16 @@ buildscript {
 }
 
 apply plugin: 'maven'
+apply plugin: 'java'
 
 repositories {
+    mavenLocal()
     mavenCentral()
 }
 
 dependencies {
-    compile "com.google.guava:guava:$guava_version"
+    // Add the top-level projects ONLY to the host project.
+    runtime project.childProjects.values().collect {
+        project(it.path)
+    }
 }

buildSrc/canonicalizer/build.gradle

@@ -0,0 +1,22 @@
+plugins {
+    id 'groovy'
+    id 'java-gradle-plugin'
+}
+
+repositories {
+    mavenLocal()
+    mavenCentral()
+}
+
+gradlePlugin {
+    plugins {
+        canonicalizerPlugin {
+            id = 'net.corda.plugins.canonicalizer'
+            implementationClass = 'CanonicalizerPlugin'
+        }
+    }
+}
+
+dependencies {
+    compile "com.google.guava:guava:$guava_version"
+}

buildSrc/settings.gradle

@@ -0,0 +1,2 @@
+rootProject.name = 'buildSrc'
+include 'canonicalizer'