Don't clang-format non checked out things

mbed-os is a directory that gets checked out by the mbed cli
(a tool similar in spirit to miot) and it contains a lot of
.c sources, so many of them that clang-format burns your CPU.

While we're at it, also fix check_no_ifdefs when running under a commit
hook.

PUBLISHED_FROM=e5dd457ea3c4f9bd880f2491fb322dffa7abf70a

examples/api_server/sqlite3.c

+/* clang-format off */
 /******************************************************************************
 ** This file is an amalgamation of many separate C source files from SQLite
 ** version 3.7.17.  By combining all the individual C code files into this 

examples/api_server/sqlite3.h

+/* clang-format off */
 /*
 ** 2001 September 15
 **