vendor: Update golang.org/x/sys/... (fixes #4615)

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/4619

vendor/golang.org/x/sys/unix/syscall_unix.go

@@ -23,6 +23,7 @@ const (
 	darwin64Bit    = runtime.GOOS == "darwin" && sizeofPtr == 8
 	dragonfly64Bit = runtime.GOOS == "dragonfly" && sizeofPtr == 8
 	netbsd32Bit    = runtime.GOOS == "netbsd" && sizeofPtr == 4
+	solaris64Bit   = runtime.GOOS == "solaris" && sizeofPtr == 8
 )
 
 // Do the interface allocations only once for common
@@ -49,6 +50,17 @@ func errnoErr(e syscall.Errno) error {
 	return e
 }
 
+// clen returns the index of the first NULL byte in n or len(n) if n contains no
+// NULL byte or len(n) if n contains no NULL byte
+func clen(n []byte) int {
+	for i := 0; i < len(n); i++ {
+		if n[i] == 0 {
+			return i
+		}
+	}
+	return len(n)
+}
+
 // Mmap manager, for use by operating system-specific implementations.
 
 type mmapper struct {