nacltest.bash: nacl/arm support.

Also detect GOARCH automatically based on `uname -m`.

LGTM=crawshaw, dave, rsc
R=rsc, iant, crawshaw, dave
CC=golang-codereviews
https://golang.org/cl/111780043

src/nacltest.bash

@@ -13,8 +13,23 @@
 set -e
 ulimit -c 0
 
+# guess GOARCH if not set
+naclGOARCH=$GOARCH
+if [ -z "$naclGOARCH" ]; then
+	case "$(uname -m)" in
+	x86_64)
+		naclGOARCH=amd64p32
+		;;
+	armv7l) # NativeClient on ARM only supports ARMv7A.
+		naclGOARCH=arm
+		;;
+	i?86)
+		naclGOARCH=386
+		;;
+	esac
+fi
+
 # Check GOARCH.
-naclGOARCH=${GOARCH:-386}
 case "$naclGOARCH" in
 amd64p32)
 	if ! which sel_ldr_x86_64 >/dev/null; then
@@ -28,6 +43,12 @@ amd64p32)
 		exit 1
 	fi
 	;;
+arm)
+	if ! which sel_ldr_arm >/dev/null; then
+		echo 'cannot find sel_ldr_arm' 1>&2
+		exit 1
+	fi
+	;;
 *)
 	echo 'unsupported $GOARCH for nacl: '"$naclGOARCH" 1>&2
 	exit 1