WIP: MSVC continued

Following up on #6230, #6349, and others. This gets past the stack overflow when compiling `inference.jl` into the system image, but craps out at `pcre.jl` because the preprocessed PCRE headers don't come out correctly from the MSVC preprocessor (it doesn't understand `-dM`). Putting this up so people can look at it, I'll keep thinking about workarounds for the preprocessor issues - can probably copy some of them straight out of the MinGW binaries. Also will write up instructions if anyone comments saying they want to try this out.