Switch to standard Java Library Plugin

This commit switches from Eclipse JDT to the
Gradle default way for building Java libraries.
diff --git a/build.gradle b/build.gradle
index 3530c63..8fd25d2 100644
--- a/build.gradle
+++ b/build.gradle
@@ -339,41 +339,16 @@
 
 configure(javaProjects + osgiProjects) {
 
-    apply plugin: 'java'
+    apply plugin: 'java-library'
     apply plugin: 'eclipse'
 
-    sourceCompatibility = '1.8'
-    targetCompatibility = '1.8'
+    java {
+        sourceCompatibility = JavaVersion.VERSION_1_8
+        targetCompatibility = JavaVersion.VERSION_1_8
+    }
 
     compileJava {
-        options.encoding = 'utf-8'
-        options.fork = true
-        doFirst {
-            options.forkOptions.with {
-                executable = 'java'
-                jvmArgs = [
-                        '-cp',
-                        configurations.ecj.asPath,
-                        'org.eclipse.jdt.internal.compiler.batch.Main',
-                        '-warn:-unused'
-                ]
-            }
-        }
-    }
-    compileTestJava {
-        options.encoding = 'utf-8'
-        options.fork = true
-        doFirst {
-            options.forkOptions.with {
-                executable = 'java'
-                jvmArgs = [
-                        '-cp',
-                        configurations.ecj.asPath,
-                        'org.eclipse.jdt.internal.compiler.batch.Main',
-                        '-warn:-unused'
-                ]
-            }
-        }
+        options.incremental = true
     }
 
     test {
@@ -382,24 +357,13 @@
         }
     }
 
-    configurations { ecj {} }
-
     dependencies {
-        ecj group: "org.eclipse.jdt.core.compiler", name: "ecj", version: ecjVersion
-
         implementation 'org.slf4j:slf4j-api'
 
         testImplementation 'junit:junit'
         testImplementation 'org.hamcrest:hamcrest-core'
         testImplementation 'org.easymock:easymock'
     }
-
-    eclipse {
-        jdt {
-            sourceCompatibility = 1.8
-            targetCompatibility = 1.8
-        }
-    }
 }
 
 configure(javaProjects + osgiProjects) {
diff --git a/gradle.properties b/gradle.properties
index 7dba76d..ea38ffd 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -1,8 +1,5 @@
 version = 3.8.0.BUILD-SNAPSHOT
 
-# Eclipse JDT Core Batch Compiler
-ecjVersion = 4.6.1
-
 # CQ4129 (PB CQ3480) JUnit Version 4.7
 junitVersion = 4.12
 
diff --git a/run_virgo_for_apache_tomcat.sh b/run_virgo_for_apache_tomcat.sh
index c60444b..b4e703c 100755
--- a/run_virgo_for_apache_tomcat.sh
+++ b/run_virgo_for_apache_tomcat.sh
@@ -1,6 +1,6 @@
 #!/bin/sh
 
-./gradlew -Dskip.normalize.bundles=true -Dskip.local.signing=true -Dskip.compress.bundles=true clean packaging:tomcat-server:installDist -x test
+./gradlew -Dskip.normalize.bundles=true -Dskip.local.signing=true -Dskip.compress.bundles=true packaging:tomcat-server:installDist -x test
 
 # build and deploy test app(s)
 
diff --git a/web/org.eclipse.virgo.web.enterprise.appdeployer/build.gradle b/web/org.eclipse.virgo.web.enterprise.appdeployer/build.gradle
index 3f89b7d..87eb158 100644
--- a/web/org.eclipse.virgo.web.enterprise.appdeployer/build.gradle
+++ b/web/org.eclipse.virgo.web.enterprise.appdeployer/build.gradle
@@ -7,6 +7,7 @@
     compile group: "org.eclipse.virgo.mirrored", name: "javax.validation", version: javaxValidationVersion, configuration: "compile", ext: "jar"
 
     compile group: "org.eclipse.virgo.mirrored", name: "org.apache.catalina", version: apacheCatalinaVersion, configuration: "compile", ext: "jar"
+    compile group: "org.eclipse.virgo.mirrored", name: "org.apache.tomcat.api", version: apacheCatalinaVersion, configuration: "compile", ext: "jar"
     compile group: "org.eclipse.virgo.mirrored", name: "org.apache.tomcat.util.scan", version: apacheCatalinaVersion, configuration: "compile", ext: "jar"
     compile group: "org.eclipse.virgo.mirrored", name: "org.apache.openejb.core", version: apacheOpenejbCoreVersion, configuration: "compile", ext: "jar"
     compile group: "org.eclipse.virgo.mirrored", name: "org.apache.openejb.jee", version: apacheOpenejbVersion, configuration: "compile", ext: "jar"