tools: add preinstall script for npm on OS X

[evanlucas]

Make sure we cleanly remove npm before installing on OS X

Related: #3606

This is working for me locally, but would be great to have some others test.

[Fishrock123]

Notes: I couldn't reproduce the original anymore, so I don't know how we can confirm this will actually work?

[evanlucas]

Good point. I'll see if I can spin up a vm and try to reproduce

[rvagg]

why are we doing a cd followed by rm and not rm with absolute path?

[evanlucas]

wow, good question. That is how the postinstall script is done. And now that I look again, it was done that way for a reason. Updating now

[rvagg]

maybe we also need a set -e if we're doing multiple lines, if the cd fails then the rm will still execute

[evanlucas]

Ok, updated with absolute path and set -e

[rvagg]

test build of this created @ https://nodejs.org/download/test/v6.0.0-test201512088ac2af7628/ if anyone else wants to review the changes

[rvagg]

I touched a bunch of TEST files under /usr/local/lib before running the installer and they still exist:

$ node -v
v6.0.0-test201512088ac2af7628
$ find /usr/local -name TEST
/usr/local/lib/node_modules/npm/node_modules/TEST
/usr/local/lib/node_modules/npm/TEST
/usr/local/lib/node_modules/TEST
/usr/local/lib/TEST

So something's not right with this as far as I can tell.

[rvagg]

Perhaps it needs to be "preupgrade" as well as "preinstall". Reading here http://s.sudre.free.fr/Stuff/PackageMaker_Howto.html but I don't know how authoritative this is.

[evanlucas]

@rvagg Ok yes it looks like neither the preinstall, nor the postinstall scripts were running. What is weird to me is that the local.pkg installs npm, so there really is no need to have an npm.pkg. Even if one deselects the npm choice, npm will still be installed. I can make it a single package and then the scripts work properly. I guess my question becomes, is it worth it? With how outdated PackageMaker.app is, I really think that we should try to get #2571 landed. Is there anything blocking that?

[Fishrock123]

@evanlucas I think the other issue mostly needs review.

[evanlucas]

Closing. Hopefully we can get the new OS X pkg stuff in soon. It should replace this anyways