Having installed MKL interferes with julia build process

[gwd999]

After having MKL installation in julia 1.6.3, which I build via make off the v1.6.3 tag, break VS Code julia-extension languageserver functionality I attempted to do a fresh julia build again from source;
so I did a git fetch to bring me up-to-date again and git checkout v1.7.0-rc1 to investigate how MKL.jl behaves with VSC and julia-v1.7.0-rc1 BUT running make then ends with

error during bootstrap:
LoadError("sysimg.jl", 19, ArgumentError("Package MKL not found in current path:\n- Run `import Pkg; Pkg.add(\"MKL\")` to install the MKL package.\n"))
require at ./loading.jl:967

make after make clean or make cleanall will end with the same error

Quite "disturbing" - some documentation on how to do a clean sweep of MKL, such that it does not produce these types of imo unexpected interferences with the julia build process would be helpful.

The only way I was able to build v1.7.0-rc1 was by deleting rm -rf julia the whole folder and doing another git clone ... of the julia repo and then executing make

[ViralBShah]

Dup of #58

Basically, on Julia 1.6, we rebuild the sysimage with MKL, which leads to all these issues. 1.7 does not have this issue since it uses LBT.