vndk-def: Use find() to find terminating char

This commit replaces naive loop with `find(b'\0', offset)`.  The
performance is improved by 3x if the script was run by a python2
interpreter.

Bug: 37867089
Test: ./tests/run.py
Change-Id: I190ebd1a2184a83216e44abdcaf7ecf7f1ed990c
Merged-In: I68d579baeab3c4c7f0928194a6c06b0969346d5f
1 file changed