cmd/toolstash: use 'go tool dist list' to get platforms

This fixes several issues:

* The ls sed hackery generates GOARCH values mipsx and mipsxle,
  instead of mips, mips64, mipsle, and mips64le.
* It removes the dependence on the 9 command.
* It marginally increases readability.

Change-Id: Ie46abc289c2c9923eed693dcf1194f4fd3ea9bd2
Reviewed-on: https://go-review.googlesource.com/38347
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
diff --git a/cmd/toolstash/buildall b/cmd/toolstash/buildall
index 65c6846..d8ec221 100755
--- a/cmd/toolstash/buildall
+++ b/cmd/toolstash/buildall
@@ -37,9 +37,12 @@
 	pattern=.
 fi
 
+targets="$(go tool dist list; echo linux/386/387)"
+targets="$(echo "$targets" | tr '/' '-' | sort | egrep "$pattern" | egrep -v 'android-arm|darwin-arm')"
+
 # put linux, nacl first in the target list to get all the architectures up front.
-targets="$((ls runtime | 9 sed -n 's/^rt0_(.*)_(.*)\.s/\1-\2/p'; echo linux-386-387) | sort | egrep -v android-arm | egrep "$pattern" | egrep 'linux|nacl')
-	$(ls runtime | 9 sed -n 's/^rt0_(.*)_(.*)\.s/\1-\2/p' | egrep -v 'android-arm|darwin-arm' | egrep "$pattern" | egrep -v 'linux|nacl')"
+targets="$(echo "$targets" | egrep 'linux|nacl') $(echo "$targets" | egrep -v 'linux|nacl')"
+
 if [ "$sete" = true ]; then
 	set -e
 fi