Enable recommended compiler warnings

Add the Java compiler option to enable the recommended compiler warnings
to the gradle and maven builds.

Author: robert-s-ubi

build.gradle

@@ -23,6 +23,14 @@ subprojects {
     apply plugin: 'maven-publish'
     apply plugin: "com.github.sherter.google-java-format"
 
+    compileJava {
+        options.compilerArgs << '-Xlint:all'
+    }
+
+    compileTestJava {
+        options.compilerArgs << '-Xlint:all'
+    }
+
     repositories {
         mavenLocal()
         maven {

pom.xml

@@ -58,6 +58,9 @@
                 <configuration>
                     <source>1.8</source>
                     <target>1.8</target>
+                    <compilerArgs>
+                        <arg>-Xlint:all</arg>
+                    </compilerArgs>
                 </configuration>
                 <version>3.14.1</version>
             </plugin>