go/build, cmd/go: add "hurd" as a GOOS value

RELNOTES=yes

Change-Id: Ie7090b5a6edd548a49bdc4295e01cb686dfe6522
Reviewed-on: https://go-review.googlesource.com/c/146023
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/cmd/go/internal/imports/build.go

@@ -207,5 +207,5 @@ func init() {
 	}
 }
 
-const goosList = "aix android darwin dragonfly freebsd js linux nacl netbsd openbsd plan9 solaris windows zos "
+const goosList = "aix android darwin dragonfly freebsd hurd js linux nacl netbsd openbsd plan9 solaris windows zos "
 const goarchList = "386 amd64 amd64p32 arm armbe arm64 arm64be ppc64 ppc64le mips mipsle mips64 mips64le mips64p32 mips64p32le ppc riscv riscv64 s390 s390x sparc sparc64 wasm "

src/go/build/syslist.go

@@ -4,5 +4,5 @@
 
 package build
 
-const goosList = "aix android darwin dragonfly freebsd js linux nacl netbsd openbsd plan9 solaris windows zos "
+const goosList = "aix android darwin dragonfly freebsd hurd js linux nacl netbsd openbsd plan9 solaris windows zos "
 const goarchList = "386 amd64 amd64p32 arm armbe arm64 arm64be ppc64 ppc64le mips mipsle mips64 mips64le mips64p32 mips64p32le ppc riscv riscv64 s390 s390x sparc sparc64 wasm "