Add support for the SUDO variable

This can be used to pick another tool to elevate privileges.

abuild-keygen.in

@@ -8,6 +8,7 @@
 
 program_version=@VERSION@
 sharedir=${ABUILD_SHAREDIR:-@sharedir@}
+SUDO="${SUDO:-sudo}"
 
 if ! [ -f "$sharedir/functions.sh" ]; then
 	echo "$sharedir/functions.sh: not found" >&2
@@ -54,11 +55,10 @@ do_keygen() {
 	)
 	openssl rsa -in "$privkey" -pubout -out "$pubkey"
 
-
 	if [ -n "$install_pubkey" ]; then
 		msg "Installing $pubkey to /etc/apk/keys..."
-		sudo mkdir -p /etc/apk/keys
-		sudo cp -i "$pubkey" /etc/apk/keys/
+		$SUDO mkdir -p /etc/apk/keys
+		$SUDO cp -i "$pubkey" /etc/apk/keys/
 	else
 
 		msg ""
@@ -101,6 +101,9 @@ usage() {
 		  -q, --quiet
 		  -h, --help           Show this help
 
+		The SUDO variable can be set to pick which tool can be used to
+		elevate privileges, if it is not set it defaults to sudo.
+
 	__EOF__
 }