cmd/dist: default to GOARM=7 on android

Auto-detecting GOARM on Android makes as little sense as for nacl/arm
and darwin/arm.

Also update androidtest.sh to not require GOARM set.

Change-Id: Id409ce1573d3c668d00fa4b7e3562ad7ece6fef5
Reviewed-on: https://go-review.googlesource.com/98875Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
Run-TryBot: Elias Naur <elias.naur@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/androidtest.bash

@@ -23,10 +23,7 @@ if [ "$GOOS" != "android" ]; then
 	exit 1
 fi
 
-if [ -z $GOARM ]; then
-	export GOARM=7
-fi
-if [ "$GOARM" != "7" ]; then
+if [ -n "$GOARM" ] && [ "$GOARM" != "7" ]; then
 	echo "android only supports GOARM=7, got GOARM=$GOARM" 1>&2
 	exit 1
 fi

src/cmd/dist/util.go

@@ -387,9 +387,9 @@ func xgetgoarm() string {
 		// NaCl guarantees VFPv3 and is always cross-compiled.
 		return "7"
 	}
-	if goos == "darwin" {
-		// Assume all darwin/arm devices are have VFPv3. This
-		// port is also mostly cross-compiled, so it makes little
+	if goos == "darwin" || goos == "android" {
+		// Assume all darwin/arm and android devices have VFPv3.
+		// These ports are also mostly cross-compiled, so it makes little
 		// sense to auto-detect the setting.
 		return "7"
 	}