ndk: Add crtbrand.c ; crtbegin_static.S includes "atexit.S" for x86/mips

"atexit" isn't defined in libc.a for x86/mips (unlike their arm's counterpart).
Include atexit.S otherwise app using atexit() may fail to link statically.

Also, add crtbegin.c to brand crtbegin_static/dynamic.c with .note.ABI-tag
section of given API level.  See $NDK/gen-platforms.sh

Change-Id: I2fdbb92119e3ca2da2c1ced6d77e63136ec35c34
4 files changed