go: a couple minor cleanups from upstream

sdk_container/src/third_party/coreos-overlay/dev-lang/go/go-9999.ebuild

@@ -55,6 +55,7 @@ go_arch()
 	local portage_arch=$(tc-arch $@)
 	case "${portage_arch}" in
 		x86)	echo 386;;
+		x64-*)	echo amd64;;
 		*)		echo "${portage_arch}";;
 	esac
 }
@@ -109,10 +110,6 @@ pkg_pretend()
 
 src_prepare()
 {
-	if [[ ${PV} != 9999 ]]; then
-		sed -i -e 's/"-Werror",//g' src/cmd/dist/build.go ||
-			die 'sed failed'
-	fi
 	epatch_user
 }