Revert "Revert "Enable ARM_PIE to fix boot""

This reverts commit bb84f6d9f34851cf3b7dcff40b1dec3110a15bcc.
TARGET_CPU_VARIANT := armv6

Implement armv6 optimized strlen from glibc 2.18
https://github.com/androidarmv6/android_bionic/commit/49f0edd14c7578affc463aec77548c12d95cac98

Change-Id: I9145c51d125c9ef70521d003788669e258fa8d2f