source rvm in GHA

Author: CamJN

macos/runtime_setup_stages/install_gems.sh

@@ -13,6 +13,7 @@ elif [[ -e $HOME/.rvm/bin/rvm-exec ]]; then
 	RVM_EXEC=$HOME/.rvm/bin/rvm-exec
 elif [ "${GITHUB_ACTIONS:-false}" = 'true' ]; then
 	\curl -sSL https://get.rvm.io | bash
+	source "$HOME/.rvm/scripts/rvm"
 	RVM_EXEC=$HOME/.rvm/bin/rvm-exec
 else
 	echo "*** ERROR: you must have RVM installed"