unix: generate linux/sparc64 go files using Docker

With cgo supporting sparc64 as of CL 102555 and CL 132155, the Docker
based build system can be used to generate file for linux/sparc64 as
well.

Updates golang/go#15282

Change-Id: I109e55f39d3229b24b0029c42074e439c6c54dc8
Reviewed-on: https://go-review.googlesource.com/c/102655
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

unix/mkall.sh

@@ -46,8 +46,8 @@ case "$#" in
 	exit 2
 esac
 
-if [[ "$GOOS" = "linux" ]] && [[ "$GOARCH" != "sparc64" ]]; then
-	# Use then new build system
+if [[ "$GOOS" = "linux" ]]; then
+	# Use the Docker-based build system
 	# Files generated through docker (use $cmd so you can Ctl-C the build or run)
 	$cmd docker build --tag generate:$GOOS $GOOS
 	$cmd docker run --interactive --tty --volume $(dirname "$(readlink -f "$0")"):/build generate:$GOOS
@@ -121,13 +121,6 @@ freebsd_arm)
 	# API consistent across platforms.
 	mktypes="GOARCH=$GOARCH go tool cgo -godefs -- -fsigned-char"
 	;;
-linux_sparc64)
-	GOOSARCH_in=syscall_linux_sparc64.go
-	unistd_h=/usr/include/sparc64-linux-gnu/asm/unistd.h
-	mkerrors="$mkerrors -m64"
-	mksysnum="./mksysnum_linux.pl $unistd_h"
-	mktypes="GOARCH=$GOARCH go tool cgo -godefs"
-	;;
 netbsd_386)
 	mkerrors="$mkerrors -m32"
 	mksyscall="go run mksyscall.go -l32 -netbsd"