CTFE using compiler intrinsics but without phobos/druntime.

[Kayo]

I like metaprogramming and I write a tons of compile-time 
evaluated code.

Important thing for me is that the usual math functions like 
`sin` from `core.math` also can be evaluated at compile time 
dispite of its source code actually does not available at compile 
time.

Now I porting my project to bare-metal. Currently there is 
nothing druntime/phobos support for that case, which means I 
cannot use `core.math` as usual.

I was trying to work around it by creating stub module similar to 
`core.math` but this does not work nor with GDC nor LDC.

Note, I do not need math at runtime I just need it for compiling.
Anyone known an easy way to get CTFE work in that case?