LUCENE-9077: Enable javac linting as in ant. TONS of warnings are currently printed.

gradle/defaults-java.gradle

@@ -5,7 +5,18 @@ allprojects {
     sourceCompatibility = "11"
     targetCompatibility = "11"
 
-    compileJava.options.encoding = "UTF-8"
-    compileTestJava.options.encoding = "UTF-8"
+    tasks.withType(JavaCompile) {
+      options.encoding = "UTF-8"
+      options.compilerArgs += [
+        "-Xlint", 
+        "-Xlint:-deprecation",
+        "-Xlint:-serial",
+
+        "-Xdoclint:all/protected",
+        "-Xdoclint:-missing", 
+        "-Xdoclint:-accessibility", 
+        "-proc:none",  // proc:none was added because of LOG4J2-1925 / JDK-8186647
+      ]
+    }
   }
 }

solr/solr-ref-guide/tools/CheckLinksAndAnchors.java

@@ -78,7 +78,7 @@ import org.jsoup.select.NodeVisitor;
  * This tool supports 2 command line options:
  * </p>
  * <ul>
- *  <li><b>-check-all-relative-links</b><br />
+ *  <li><b>-check-all-relative-links</b>
  *    <p>By default, only relative links to files in the same directory (ie: not startin with
  *       <code>"../"</code> are checked for existence.  This means that we can do a "quick" validatation of
  *       links to other ref-guide files, but ignore relative links to things outside of the ref-guide --
@@ -86,7 +86,7 @@ import org.jsoup.select.NodeVisitor;
  *       <em>also</em> check relative links where the path starts with <code>"../"</code>
  *    </p>
  *  </li>
- *  <li><b>-bare-bones</b><br/>
+ *  <li><b>-bare-bones</b>
  *    <p>By default, this tool assumes it is analyzing Jekyll generated files.  If this option is specified,
  *       then it instead assumes it's checking "bare bones" HTML files...
  *    </p>