Use java_home to determine jdk location.

Specifying the major version rather than hard coding
to a minor version.

Change-Id: Ieccec98c1b41e3eb7f512bcebc83f6034d634862
diff --git a/envsetup.sh b/envsetup.sh
index 0c8ae30..6891747 100644
--- a/envsetup.sh
+++ b/envsetup.sh
@@ -1407,7 +1407,7 @@
       else
         case `uname -s` in
             Darwin)
-                export JAVA_HOME=/Library/Java/JavaVirtualMachines/jdk1.7.0_51.jdk/Contents/Home
+                export JAVA_HOME=$(/usr/libexec/java_home -v 1.7)
                 ;;
             *)
                 export JAVA_HOME=/usr/lib/jvm/java-7-openjdk-amd64