allow passing command line flags to `compilecache`. (#53316) (#240)
Pkg right now has to start a separate process to run precompilation for
the test environment which is annoying for multiple reasons
Corresponding Pkg PR: https://github.com/JuliaLang/Pkg.jl/pull/3792
Co-authored-by: Kristoffer Carlsson <kcarlsson89@gmail.com>