compilert-rt: build out-of-line LSE atomics helpers for aarch64

Both clang >= 12 and gcc >= 10.1 now default to -moutline-atomics for
aarch64. This requires a bunch of helper functions in libcompiler_rt.a,
to avoid link errors like "undefined symbol: __aarch64_ldadd8_acq_rel".

(Note: of course you can use -mno-outline-atomics as a workaround too,
but this would negate the potential performance benefit of the faster
LSE instructions.)

Bump __FreeBSD_version so ports maintainers can easily detect this.

PR:		257392
MFC after:	2 weeks

lib/libcompiler_rt/Makefile

@@ -19,6 +19,26 @@ MK_WERROR.gcc=	no
 
 .include "Makefile.inc"
 
+# Out-of-line LSE atomics helpers for aarch64
+.if ${MACHINE_CPUARCH} == "aarch64"
+. for pat in cas swp ldadd ldclr ldeor ldset
+.  for size in 1 2 4 8 16
+.   for model in 1 2 3 4
+.    if ${pat} == "cas" || ${size} != "16"
+# Use .for to define lse_name, to get a special loop-local variable
+.     for lse_name in outline_atomic_${pat}${size}_${model}.S
+CLEANFILES+=	${lse_name}
+STATICOBJS+=	${lse_name:R}.o
+ACFLAGS.${lse_name}+= -DL_${pat} -DSIZE=${size} -DMODEL=${model} -I${CRTSRC}
+${lse_name}: lse.S
+	ln -sf ${.ALLSRC} ${.TARGET}
+.     endfor # lse_name
+.    endif
+.   endfor # model
+.  endfor # size
+. endfor # pat
+.endif
+
 .if ${MK_INSTALLLIB} != "no"
 SYMLINKS+=	libcompiler_rt.a ${LIBDIR}/libgcc.a
 .endif

sys/sys/param.h

@@ -76,7 +76,7 @@
  * cannot include sys/param.h and should only be updated here.
  */
 #undef __FreeBSD_version
-#define __FreeBSD_version 1400026
+#define __FreeBSD_version 1400027
 
 /*
  * __FreeBSD_kernel__ indicates that this system uses the kernel of FreeBSD,