BUILD: atomic: atomic.h may need compiler.h on ARMv8.2-a

BUILD: atomic: atomic.h may need compiler.h on ARMv8.2-a

We get a build error in ncbuf.c when building for ARMv8.2-a because ncbuf
has minimal includes and among them bug.h which includes atomic.h. Atomic.h
may use "forceinline" without including compiler.h, hence the build error.
It was verified that adding it doesn't inflate the total headers.

Since all other C files include api.h which already covers this, there's
no real need to bapkport this. The issue was already there in 2.3 though.