androidbp: make error handling stricter

Instead of putting errors into the translated Android.mk file where
they are unlikely to be seen and may cause strange build behavior,
make all errors fatal.  Also buffer to a byte buffer and then write
to the output file once we are sure there are no errors.

Change-Id: I247f405dd0a7c1d14c2681f86c7ac626e035ac2c
3 files changed