codesign fails on Yosemite 10.10.3

[hongrich]

After upgrading OS X to 10.10.3 and Xcode to 6.3 yesterday, it seems that signing the entire app bundle with --deep no longer works. Signing the included frameworks and apps individually according this fixes the problem. Related to #171 and #720

[asamiller]

I'm also having an issue signing after updating to 10.10.3 and Xcode 6.3. I'm running:

codesign --verbose --deep --force --sign "<DEV ID>" build/Atom.app
and get
build/Atom.app: invalid or unsupported format for signature In subcomponent: /Users/asa/app/Atom.app/Contents/Frameworks/Squirrel.framework

[zcbenz]

I think signing individual frameworks and apps has always been the correct way to go. I'm closing this since this is a problem of OS X, not something we can fix in atom-shell.

There are also some instructions on code signing in nw.js's issues:
nwjs/nw.js#3258
nwjs/nw.js#616