Make test-compilation and test-running pass

The netty-buffer test-jar dependency was causing some problems, but this works around that.

pom.xml

@@ -74,9 +74,6 @@
     <junit.version>5.7.0</junit.version>
     <surefire.version>3.0.0-M5</surefire.version>
     <skipTests>false</skipTests>
-    <argLine.java9.extras />
-    <!-- Export some stuff which is used during our tests -->
-    <argLine.java9>--illegal-access=deny ${argLine.java9.extras}</argLine.java9>
     <argLine.common>
       -server
       -dsa -da -ea:io.netty...
@@ -95,9 +92,21 @@
       </extension>
     </extensions>
     <plugins>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-dependency-plugin</artifactId>
+        <version>3.1.2</version>
+        <executions>
+          <execution>
+            <goals>
+              <goal>properties</goal>
+            </goals>
+          </execution>
+        </executions>
+      </plugin>
       <plugin>
         <artifactId>maven-compiler-plugin</artifactId>
-        <version>3.8.0</version>
+        <version>3.8.1</version>
         <configuration>
           <compilerVersion>${java.version}</compilerVersion>
           <fork>true</fork>
@@ -115,6 +124,10 @@
             <arg>--add-modules</arg>
             <arg>jdk.incubator.foreign</arg>
           </compilerArgs>
+          <!-- Add the test-jar classes to the io.netty.buffer module for test-compile. -->
+          <testCompilerArgument>
+            --patch-module io.netty.buffer=${io.netty:netty-buffer:test-jar:tests}
+          </testCompilerArgument>
           <excludes>
             <exclude>**/package-info.java</exclude>
           </excludes>
@@ -165,7 +178,7 @@
             <include>**/*Test*.java</include>
           </includes>
           <runOrder>random</runOrder>
-          <argLine>${argLine.common} ${argLine.printGC} ${argLine.java9} --add-modules jdk.incubator.foreign</argLine>
+          <argLine>${argLine.common} ${argLine.printGC} --illegal-access=deny --patch-module io.netty.buffer=${io.netty:netty-buffer:test-jar:tests} --add-modules jdk.incubator.foreign</argLine>
           <!-- Ensure the whole stacktrace is preserved when an exception is thrown. See https://issues.apache.org/jira/browse/SUREFIRE-1457 -->
           <trimStackTrace>false</trimStackTrace>
         </configuration>