update dependencies

vendor/golang.org/x/sys/unix/mksyscall.pl

@@ -69,6 +69,16 @@ if($ARGV[0] =~ /^-/) {
 	exit 1;
 }
 
+# Check that we are using the new build system if we should
+if($ENV{'GOOS'} eq "linux" && $ENV{'GOARCH'} ne "sparc64") {
+	if($ENV{'GOLANG_SYS_BUILD'} ne "docker") {
+		print STDERR "In the new build system, mksyscall should not be called directly.\n";
+		print STDERR "See README.md\n";
+		exit 1;
+	}
+}
+
+
 sub parseparamlist($) {
 	my ($list) = @_;
 	$list =~ s/^\s*//;
@@ -300,7 +310,7 @@ if($errors) {
 
 print <<EOF;
 // $cmdline
-// MACHINE GENERATED BY THE COMMAND ABOVE; DO NOT EDIT
+// Code generated by the command above; see README.md. DO NOT EDIT.
 
 // +build $tags