androidtest.bash: don't require GOARCH set

The host GOARCH is most likely supported (386, amd64, arm, arm64).

Change-Id: I86324b9c00f22c592ba54bda7d2ae97c86bda904
Reviewed-on: https://go-review.googlesource.com/99155
Run-TryBot: Elias Naur <elias.naur@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>

src/androidtest.bash

@@ -27,10 +27,6 @@ if [ -n "$GOARM" ] && [ "$GOARM" != "7" ]; then
 	echo "android only supports GOARM=7, got GOARM=$GOARM" 1>&2
 	exit 1
 fi
-if [ "$GOARCH" = "" ]; then
-	echo "GOARCH must be set" 1>&2
-	exit 1
-fi
 
 export CGO_ENABLED=1
 unset GOBIN