fix(ubuntu/arm*): detect non amd64 ubuntu and handle

If we're running Ubuntu on non-amd64 we get an install error.  As there's
no ARM package yet we can offer the user the option to install via cargo
rather than install something that won't work.

install.sh

@@ -64,18 +64,22 @@ __atuin_install_arch(){
 }
 
 __atuin_install_ubuntu(){
-	echo "Ubuntu detected"
-	# TODO: select correct AARCH too
-	ARTIFACT_URL="https://github.com/ellie/atuin/releases/download/$LATEST_VERSION/atuin_${LATEST_VERSION//v/}_amd64.deb"
-
-	TEMP_DEB="$(mktemp)".deb &&
-	curl -Lo "$TEMP_DEB" "$ARTIFACT_URL"
-	if command -v sudo &> /dev/null; then
-		sudo apt install "$TEMP_DEB"
+	if [ "$(dpkg --print-architecture)" = "amd64" ]; then
+		echo "Ubuntu detected"
+		ARTIFACT_URL="https://github.com/ellie/atuin/releases/download/$LATEST_VERSION/atuin_${LATEST_VERSION//v/}_amd64.deb"
+
+		TEMP_DEB="$(mktemp)".deb &&
+		curl -Lo "$TEMP_DEB" "$ARTIFACT_URL"
+		if command -v sudo &> /dev/null; then
+			sudo apt install "$TEMP_DEB"
+		else
+			su -l -c "apt install '$TEMP_DEB'"
+		fi
+		rm -f "$TEMP_DEB"
 	else
-		su -l -c "apt install '$TEMP_DEB'"
+		echo "Ubuntu detected, but not amd64"
+		__atuin_install_unsupported
 	fi
-	rm -f "$TEMP_DEB"
 }
 
 __atuin_install_linux(){
@@ -148,7 +152,7 @@ __atuin_install_cargo(){
 }
 
 __atuin_install_unsupported(){
-	echo "Unknown or unsupported OS"
+	echo "Unknown or unsupported OS or architecture"
 	echo "Please check the README at https://github.com/ellie/atuin for manual install instructions"
 	echo "If you have any problems, please open an issue!"