Add MAVEN_OPTS build workaround to DEVNOTES for 1.2.0

git-svn-id: https://svn.apache.org/repos/asf/flume/trunk@1360064 13f79535-47bb-0310-9956-ffa450edef68

DEVNOTES

@@ -39,6 +39,23 @@ We are using Maven v3.x.  The Maven build system steps through several phases
 to create build artefacts.  At the highest level, the phases that are relevent
 to most devs are "compile" -> "test" -> "package" -> "install".
 
+Set MAVEN_OPTS to give the Flume build enough RAM to build.
+
+  export MAVEN_OPTS="-Xmx512M -XX:MaxPermSize=512M"
+
+Note: If you see a permgen error (below), you need to increase the perm gen size.
+
+[ERROR] PermGen space -> [Help 1]
+[ERROR] 
+[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
+[ERROR] Re-run Maven using the -X switch to enable full debug logging.
+[ERROR] 
+[ERROR] For more information about the errors and possible solutions, please read the following articles:
+[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/OutOfMemoryError
+
+Builds
+------
+
 A development build that runs unit tests and installs to local Maven repo.
 This builds and tests all plugins.