atlas: use compiler_blacklist_versions portgroup

[ryandesign (Ryan Carsten Schmidt)]

The atlas port has this block of code in the +clang variant:

    if {[vercmp $xcodeversion 4.3] < 0} {
        pre-fetch {
            return -code error "Your version of clang is too old!"
        }
    }

This is not the correct way to check for this. You need to check the clang version, not the Xcode version, because the user could have updated Xcode but forgotten to update the command line tools; this happens all the time because users do not know that they need to actually open the Xcode application in order for the command line tools to get updated.

Use the compiler_blacklist_versions​ portgroup to blacklist the specific range of Xcode clang versions that will not work for atlas. If the clang is older, then MacPorts will use llvm-gcc-4.2 instead. XcodeVersionInfo lists some known clang versions.

It's odd to have a +clang variant at all and it seems like you could remove it. MacPorts will automatically choose to use clang on Xcode 4.2 and later anyway.

[cooljeanius (Eric Gallager)]

Cc Me!

[Veence (Vincent)]

Ok Ryan. As soon as the other bugs are fixed, I’ll enhance the Portfile according to your hint.

[petrrr]

Cc Me!

[kencu (Ken)]

The atlas port no longer contains this block.