Prevent bs-platform from being rebuild every time when running yarn add

[sgronblo]

Trying to write a small test app using bucklescript-tea. I noticed that every time I ran something like yarn add @types/webpack ie. entirely unrelated to Bucklescript, bs-platform was being rebuilt every time any way.

After asking about this on the ReasonML discourse it turns out that this is a known "bug" with yarn where it apparently calls packages' postinstall script every time: yarnpkg/yarn#932

Somebody on the Discourse was saying that packages would need to work around this currently by creating a file to represent having built already and then checking if that file exists on subsequent runs. Would this make sense to add to bs-platform until this problem is fixed?

[bobzhang]

I am fine with work around, if we add a build stamp file, how do we run postinstall explicitly? by manually removing the build stamp file?