A trick to bypass julia #14577?

[Non-Contradiction]

Because of julia issue #14577,
non-precompiled packages cannot be imported in embedding julia v0.6,
so currently using XXX in JuliaCall doesn't work if package XXX is non-precompiled.
This problem results in many other problems, related to #10 #34 #40 for example.

This problem exists because of the incorrect JULIA_HOME for embedding julia.
I read the source of julia, and find that functions like Base.compilecache depends on function julia_cmd, and inspired by Revise.jl, we can actually use @eval Base julia_cmd() = ..... to modify this function to be the correct version to "solve" this problem in a tricky way, for example:

> julia_command('Base.compilecache("Suppressor")')
INFO: Precompiling module Suppressor.
Error happens in Julia.
could not spawn `/Applications/Julia-0.6.app/Contents/Resources/julia/lib/julia -Ccore2 -J/Applications/Julia-0.6.app/Contents/Resources/julia/lib/julia/sys.dylib --compile=yes --depwarn=yes -O0 --output-ji /Users/lichangcheng/.julia/lib/v0.6/Suppressor.ji --output-incremental=yes --startup-file=no --history-file=no --color=no --eval 'while !eof(STDIN)
    eval(Main, deserialize(STDIN))
end
'`: permission denied (EACCES)
Stacktrace:
 [1] _jl_spawn(::String, ::Array{String,1}, ::Ptr{Void}, ::Base.Process, ::Base.PipeEndpoint, ::Ptr{Void}, ::Ptr{Void}) at ./process.jl:360
 [2] #374 at ./process.jl:512 [inlined]
 [3] setup_stdio(::Base.##374#375{Cmd}, ::Tuple{Pipe,Base.PipeEndpoint,Base.PipeEndpoint}) at ./process.jl:499
 [4] #spawn#373(::Nullable{Base.ProcessChain}, ::Function, ::Cmd, ::Tuple{Pipe,Base.PipeEndpoint,Base.PipeEndpoint}) at ./process.jl:511
 [5] (::Base.#kw##spawn)(::Array{Any,1}, ::Base.#spawn, ::Cmd, ::Tuple{Pipe,Base.PipeEndpoint,Base.Pip
> julia_command('Base.julia_cmd()')
`/Applications/Julia-0.6.app/Contents/Resources/julia/lib/julia -Ccore2 -J/Applications/Julia-0.6.app/Contents/Resources/julia/lib/julia/sys.dylib --compile=yes --depwarn=yes`
  
> julia_command('@eval Base julia_cmd() = `/Applications/Julia-0.6.app/Contents/Resources/julia/bin/julia -Ccore2 -J/Applications/Julia-0.6.app/Contents/Resources/julia/lib/julia/sys.dylib --compile=yes --depwarn=yes`')
WARNING: Method definition julia_cmd() in module Base at util.jl:604 overwritten at none:1.
julia_cmd (generic function with 2 methods)
  
> julia_command('Base.compilecache("Suppressor")')
INFO: Precompiling module Suppressor.
"/Users/lichangcheng/.julia/lib/v0.6/Suppressor.ji"

I'm wondering if this kind of method worths the trouble it may bring.
Any opinion is welcomed.

[Non-Contradiction]

After consideration and testing, I think the approach is okay, because it just does what should be done, and it is really useful. Commit 3167c5a implements the approach.