Enable CI build to be run manually and add download libs step

Via 'workflow_dispatch' users with the necessary access rights can now
run the GitHub Actions workflow from the web UI.

Still in testing stage in redundant module 'libx', prepare for the
future situation that currently committed binaries in 'lib' shall be
replaced by downloaded ones.

Signed-off-by: Alexander Kriegisch <Alexander@Kriegisch.name>

.github/workflows/maven.yml

@@ -1,13 +1,14 @@
 # This workflow will build a Java project with Maven
 # For more information see: https://help.github.com/actions/language-and-framework-guides/building-and-testing-java-with-maven
 
-name: Java CI with Maven
+name: Build AspectJ
 
 on:
   push:
     branches: [ master ]
   pull_request:
     branches: [ master ]
+  workflow_dispatch:
 
 jobs:
   build:
@@ -30,6 +31,9 @@ jobs:
           ./mvnw -B --version
           ant -version
 
+      - name: Download + install test libraries
+        run: ./mvnw -B --file libx/pom.xml compile
+
       - name: Compile code
         run: ./mvnw -B -DskipTests package --file pom.xml