Lightweight printf-compatible format processing library

通用makefile，支持多级目录

google android open source code, this os is used for sensorhub, google named chre, a eventbased os; prot this os to arm920t, include some module: 1. startup 2. interrupt 3. atomic 4. spinlock 5. timer 6. printf 7. serial 8. codingstyle tool an os based this can run in a board

Minimal printf() implementation for embedded projects.