DEV: Run `yarn install` when running `bin/ember-cli` (#13102)

DEV: Run yarn install when running bin/ember-cli (#13102)

Some people have noticed that if we change the packages in package.json that they have to manually run yarn install or Discourse won’t work.

This adds yarn install to the bin/ember-cli helper we run. It seems quite fast if there is nothing to install so it shouldn’t hurt to do this every time we start the server.

diff --git a/bin/ember-cli b/bin/ember-cli
index 3aa799e..1395ecc 100755
--- a/bin/ember-cli
+++ b/bin/ember-cli
@@ -43,4 +43,5 @@ if !args.include?("--proxy")
   args << PROXY
 end
 
+system "yarn install --cwd #{yarn_dir}"
 exec "yarn", *args.to_a.flatten

GitHub sha: f165f98c