runtime: use pthread_sigmask, not sigprocmask, on Darwin ARM/ARM64

Other systems use pthread_sigmask.  It was a mistake to use sigprocmask
here.

Change-Id: Ie045aa3f09cf035fcf807b7543b96fa5b847958a
Reviewed-on: https://go-review.googlesource.com/16720Reviewed-by: Dave Cheney <dave@cheney.net>
Reviewed-by: David Crawshaw <crawshaw@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/runtime/sys_darwin_arm.s

@@ -24,9 +24,9 @@
 #define	SYS_kill           37
 #define	SYS_getpid         20
 #define	SYS___pthread_kill 328
+#define	SYS_pthread_sigmask 329
 #define	SYS_setitimer      83
 #define	SYS___sysctl       202
-#define	SYS_sigprocmask    48
 #define	SYS_sigaction      46
 #define	SYS_sigreturn      184
 #define	SYS_select         93
@@ -268,7 +268,7 @@ TEXT runtime·sigprocmask(SB),NOSPLIT,$0
 	MOVW	sig+0(FP), R0
 	MOVW	new+4(FP), R1
 	MOVW	old+8(FP), R2
-	MOVW	$SYS_sigprocmask, R12
+	MOVW	$SYS_pthread_sigmask, R12
 	SWI	$0x80
 	BL.CS	notok<>(SB)
 	RET

src/runtime/sys_darwin_arm64.s

@@ -24,9 +24,9 @@
 #define	SYS_kill           37
 #define	SYS_getpid         20
 #define	SYS___pthread_kill 328
+#define	SYS_pthread_sigmask 329
 #define	SYS_setitimer      83
 #define	SYS___sysctl       202
-#define	SYS_sigprocmask    48
 #define	SYS_sigaction      46
 #define	SYS_sigreturn      184
 #define	SYS_select         93
@@ -256,7 +256,7 @@ TEXT runtime·sigprocmask(SB),NOSPLIT,$0
 	MOVW	sig+0(FP), R0
 	MOVD	new+8(FP), R1
 	MOVD	old+16(FP), R2
-	MOVW	$SYS_sigprocmask, R16
+	MOVW	$SYS_pthread_sigmask, R16
 	SVC	$0x80
 	BCC	2(PC)
 	BL	notok<>(SB)