ALLJOYN-1973: Tweak setting environment logic when ANDROID_PROXIMITY=on.

This is fallout from changes to build_core for this ticket.

Change-Id: If53929083341298e8859afbc59a61d3187f32ce8
Exit with a fail code from SCons files in the case of an error.

Change-Id: If07fcbc3ad7f450a645583f77887a0c035229152
ALLJOYN-1973 When building with ICE=on we must modify the JAVACLASSPATH

This now properly appends Android.jar to the JAVACLASSPATH when building
with ICE=on

Change-Id: I2af3046f53f7139bad7a189a59d66a265f671643