Bubble up failures in dotfiles installation

Currently, if the dotfiles installation (`coder dotfiles ...`) fails, the script still shows as successful in the Coder UI.

dotfiles/run.sh

@@ -20,4 +20,7 @@ if [ -n "$${DOTFILES_URI// }" ]; then
     DOTFILES_USER_HOME=$(eval echo ~"$DOTFILES_USER")
     sudo -u "$DOTFILES_USER" sh -c "'$CODER_BIN' dotfiles '$DOTFILES_URI' -y 2>&1 | tee '$DOTFILES_USER_HOME'/.dotfiles.log"
   fi
+  if [ $? -ne 0 ]; then
+    echo "Failed to install dotfiles"
+    exit 1  
 fi