Check for pods first, don't double up on yarn install(s)

[rickycodes]

On linux the yarn clean command does not exit correctly:

yarn clean
...
2. Create xcconfig files...
3. Init git submodules
This may take a while...
/bin/sh: 1: pod: not found
error Command failed with exit code 127.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

I don't have pods on my computer, so i can't install them. this has bitten me a couple times when I've tried to chain off of (&&) yarn clean

eg: yarn clean && echo "now I am happy"

checking for the pod command first means now I am happy:

$ yarn clean && echo "now I am happy"
yarn run v1.22.4
...
2. Create xcconfig files...
3. Init git submodules
This may take a while...
$ command -v pod && (cd ios/ && pod install && cd ..) || echo "pod command not found"
pod command not
Done in 22.50s.
now I am happy

we were also doubling up on yarn installs in the clean flow for no reason, clean:node handles a new yarn install so it's pointless to do it again after that.

[andrepimenta]

Niiice!