Older versions of Xcode Command Line Tools on macOS Catalina I have a project that requires the Command Line Tools from macOS
High Sierra. The specific installer I’m running is Command Line Tools (macOS High Sierra version 10.13).pkg.

When I run it, I get:


  “This package is incompatible with this version of macOS. The package is trying to install content to the system volume. Contact the software manufacturer for assistance.”


I haven’t contacted Apple about this yet. My queries are:


Should I just install this on a different drive?
Is there a way to get this to install to my main internal SSD?
Once installed, what's the easiest way to switch between the old Command Line Tools and new Command Line Tools when I need to?
The command-line tool installer installs lots of stuff (libraries, frameworks, etc.) in multiple OS system directories.  So you probably need to find or create a volume (external drive or partition) with OS X High Sierra on it for the install to complete.

I usually partition my SSDs so that I can keep multiple bootable macOS versions on it for running such older tooling and apps.