add option to test using local CF build

build.gradle

@@ -43,6 +43,19 @@ dependencies {
   testImplementation libs.checkerframework.framework
 }
 
+// To use a locally-built Checker Framework, run gradle with "-PcfLocal".
+if (hasProperty('cfLocal')) {
+  def cfHome = String.valueOf(System.getenv('CHECKERFRAMEWORK'))
+  println cfHome
+  dependencies {
+    testImplementation files(cfHome + '/checker/dist/checker.jar')
+    testImplementation files(cfHome + '/framework-test/build/libs/framework-test-3.42.0-eisop3-SNAPSHOT.jar')
+
+    // Need plume-util dependency to typecheck conformance tests 
+    testImplementation 'org.plumelib:plume-util:1.9.0'
+  }
+}
+
 spotless {
   format 'misc', {
     // define the files to apply `misc` to