Refuse to run if install_name_tool is broken

[ryandesign (Ryan Carsten Schmidt)]

I was just reminded that ​Apple shipped a broken install_name_tool in Xcode 12.2, the first Xcode version for Big Sur. Any ports whose builds involve the use of install_name_tool on a symlink will probably succeed but will be wrong. This is a pain to diagnose when it happens. It would be impractical to analyze all ports to determine which ones use install_name_tool and update them individually to prevent the use of the bad install_name_tool. I'd like to propose that, if MacPorts doesn't already do this, it should check the version of Xcode and/or command line tools, and if it's one that has the broken install_name_tool, it should simply refuse to install any port and require the user to upgrade to a non-broken version. I think this will save some grief.

I know Xcode 12.2 was affected. I don't know whether 12.3 was affected. I believe 12.4 was no longer affected. Apple never responded to my bug report to indicate when it was fixed. I was going to try downloading those command line tools versions, extracting install_name_tool from them, and testing to see which versions were affected.