Hello,

in order to get GSLL to run on Windows7+CCL+MSYS2+GSL, I needed to customize *cc* and *cc-flags*.  Right now, I do this by modifying the code in grovel.lisp, as for *cc-flags*:

   #+(and windows msys2)
   (list "-I" "E:/msys64/mingw64/lib/libffi-3.2.1/include/"
         "-I" "c:/Users/977315/quicklisp/dists/quicklisp/software/cffi_0.14.0/")


(I prefer not to modify system-wide environment variables on my PC)

I see alternate ways of achieving the same effect:
  1. Write own gsll loader that customizes *cc* and *cc-flags*
  2. Write own cffi-libffi loader that customizes the variables
  3. (somehow) advise gsll or cffi-libffi loaders in my lisp-init files to customize the variables
  4. Modify environment variables for my process.
What is the advised way to do this?  I would prefer 3: in my lisp startup file, I (somehow) write some advice code to asdf that customize *cc* and *cc-flags*.  But I don't know how to do that.

Thank you,

Mirko