I know there are people here at Mozilla who have been building Firefox on Lion releases for a while now, but I couldn’t find anything that described all the problems. So here I am.

TL;DR: Reinstall XCode & apply a couple patches.

Mercurial

I had originally installed Mercurial via easy_install, so your results may be different. Regardless it was broken. Apparently you can edit the executable and it works, but I didn’t try. Attempting to install Mercurial again failed with Python headers are required to build Mercurial.

Reinstall XCode then reinstall Mercurial and you’re set.

make Not Found

Reinstalling XCode fixes that too.

Build Fails with expected initializer before ‘NS_NORETURN’

Your build will probably fail. The patch in bug 655339 works to get past this.

Build Fails with $MACOSX_DEPLOYMENT_TARGET mismatch error

distutils.errors.DistutilsPlatformError: $MACOSX_DEPLOYMENT_TARGET mismatch: now "10.6" but "10.7" during configure

I first thought this was a problem with specifying the wrong target SDK, but I was wrong. This is apparently a python bug. Bug 659881 has more details (and a workaround patch). The bug talks about python via MacPorts, but I’m not using MacPorts nor any non-default python installs.