build: Allow building with OpenJDK v1.7

Ubuntu-12.10 ships with OpenJDK v1.7 and AOSP errors out if you try
to build it with JAVA version other than 1.6. Linaro Android build
with JAVA v1.7, boot tested on Origen 4412, seems to work fine.

Change-Id: I8ca783b48de80131f830139a33d8fc0aa92c562c
add support for overriding build.prop settings
comment out the build date assert
Debugging TRUE
Dexpreopt FALSE
Compiler customizations

option:  Add SaberMod GCC 4.8 androideabi as a BoardConfig
To enable add USE_SABERMOD_ANDROIDEABI_48 := true
to your BoardConfig.mk of a SaberMod supported device

Signed-off-by:  Paul Beeler <sparksco@gmail.com>