Update execution environment and require mvn version.

Change-Id: I9c6c4001a58523f8ace29ef0564cb348de312426
Signed-off-by: Greg Watson <g.watson@computer.org>
diff --git a/org.eclipse.photran.target/photran.target b/org.eclipse.photran.target/photran.target
index e0d2d1a..2086061 100644
--- a/org.eclipse.photran.target/photran.target
+++ b/org.eclipse.photran.target/photran.target
@@ -10,7 +10,7 @@
 <repository location="http://download.eclipse.org/cbi/updates/license/"/>
 </location>
 <location includeAllPlatforms="false" includeConfigurePhase="true" includeMode="planner" includeSource="true" type="InstallableUnit">
-<unit id="org.eclipse.sdk.ide" version="0.0.0"/>
+<unit id="org.eclipse.sdk.feature.group" version="0.0.0"/>
 <repository location="http://download.eclipse.org/eclipse/updates/4.19/R-4.19-202103031800/"/>
 </location>
 <location includeAllPlatforms="false" includeConfigurePhase="true" includeMode="planner" includeSource="true" type="InstallableUnit">
@@ -18,4 +18,11 @@
 <repository location="https://download.eclipse.org/tools/cdt/releases/10.3/cdt-10.3.0/"/>
 </location>
 </locations>
+<targetJRE path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-11"/>
+<launcherArgs>
+<vmArgs>-Xms40m&#13;
+-Xmx512M&#13;
+-ea</vmArgs>
+<programArgs>-consolelog</programArgs>
+</launcherArgs>
 </target>
diff --git a/pom.xml b/pom.xml
index 1362387..33aa289 100644
--- a/pom.xml
+++ b/pom.xml
@@ -15,6 +15,11 @@
 	<name>PTP Photran Parent</name>
 
 	<properties>
+		<!-- Maven 3.6.1 and 3.6.2 do not work with Tycho, see Bug 551674
+		     CDT enforces a minimum of 3.6.3 because that is what CDT's CI
+			 runs with. It may work with older versions, but this is not
+			 tested or supported. -->
+		<required-maven-version>3.6.3</required-maven-version>
 		<tycho-version>2.3.0</tycho-version>
 		<tycho-extras-version>${tycho-version}</tycho-extras-version>
 		<cbi-plugins.version>1.3.1</cbi-plugins.version>
@@ -61,6 +66,32 @@
 	<build>
 		<plugins>
 			<plugin>
+				<inherited>true</inherited>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-enforcer-plugin</artifactId>
+				<version>3.0.0-M3</version>
+				<executions>
+				<execution>
+					<id>enforce-maven-version</id>
+					<goals>
+						<goal>enforce</goal>
+					</goals>
+					<configuration>
+						<rules>
+							<requireMavenVersion>
+								<version>${required-maven-version}</version>
+							</requireMavenVersion>
+							<requireJavaVersion>
+								<version>11</version>
+							</requireJavaVersion>
+						</rules>
+						<fail>true</fail>
+						<failFast>true</failFast>
+					</configuration>
+				</execution>
+				</executions>
+			</plugin>
+			<plugin>
 				<groupId>org.eclipse.tycho</groupId>
 				<artifactId>tycho-maven-plugin</artifactId>
 				<version>${tycho-version}</version>