After r364753, there should be no need to suppress -Watomic-alignment

warnings anymore for compiler-rt's atomic.c. This occurred because the
IS_LOCK_FREE_8 macro was not correctly defined to 0 for mips, and this
caused the compiler to emit a runtime call to __atomic_is_lock_free(),
and that triggers the warning.

MFC after:	2 weeks
X-MFC-With:	r364753

lib/libcompiler_rt/Makefile.inc

@@ -1,7 +1,5 @@
 # $FreeBSD$
 
-.include <bsd.compiler.mk>
-
 CRTARCH=	${MACHINE_CPUARCH:C/amd64/x86_64/}
 
 CRTSRC=		${SRCTOP}/contrib/llvm-project/compiler-rt/lib/builtins
@@ -125,10 +123,6 @@ SRCF+=		umoddi3
 SRCF+=		umodsi3
 SRCF+=		umodti3
 
-.if "${COMPILER_TYPE}" == "clang"
-CFLAGS.atomic.c+=      -Wno-atomic-alignment
-.endif
-
 # Avoid using SSE2 instructions on i386, if unsupported.
 .if ${MACHINE_CPUARCH} == "i386" && empty(MACHINE_CPU:Msse2)
 SRCS+=		floatdidf.c