Increase max heap size for javac to 2GB.

Compiling Dialer requires increasing the javac heap size above
1GB, probably due to the extensive use of annotation processors.
Increase it to 2GB.

Test: m -j ANDROID_COMPILE_WITH_JACK=false
Change-Id: I4dd3759a98ea915469e69f563dc49be8a25d518e
Merged-In: I4dd3759a98ea915469e69f563dc49be8a25d518e
(cherry picked from commit 0e785c79)