That was a clean build for the binary code used in Tcl scripts, every time someone would sync their local development with latests, or switch code branches.

Plenty of code was Tcl scritping, and when re-compiling C code, only the affected set of files would be re-compiled, everything else was kept around in object files and binary libraries, and if not affected only required re-linking.

That’s probably why tcl is in there, you use uncompiled scripting to orchestrate the native code, which is the part that takes hours to compile.