[Development] [Announce] Changes to building Qt on Mac OS X

[Tor Arne Vestbø]

Hi,

A few changes has been made in how we build Qt on Mac OS X that people 
should be aware of when building 5.1 from source:

  - The '-sdk' option to configure now takes a named SDK, as reported by 
xcodebuild, eg. macosx, macosx10.7, iphoneos, etc -- not a path. This 
applies to QMAKE_MAC_SDK as well, so any pro file checks should be 
updated (outside of qtbase).

  - We always build against an SDK, as recommended by Apple, even if 
you're not passing -sdk explicitly. By default we choose the latest one 
provided by Xcode.

  - We use the Xcode-provided toolchain for eg. clang, g++, etc, instead 
of the tools in your PATH.

These changes together allow us to trust the environment we're building 
against, whereas before you could have a mismatch between the Xcode 
installation and the developer tools installed in /usr that resulted in 
sneaky build breaks. It also allows us to provide Clang as an option 
when building on 10.6, as the choice is not dependent on the OSX version 
but the Xcode version (and hence toolchain availability).

I will add some more checks to configure to verify that the Xcode 
installation is sane before we try using it, but for now you can check 
yourself using:

   xcrun g++ -v

If it fails, run xcode-select --switch and point it to eg:

   /Applications/Xcode.app/Contents/Developer


Tor Arne