ccwrap massages the compiler's standard include directories to remove
'/usr/include/w32api', with the intent of allowing it to be overriden by
'--with-windows-headers' (See 4c36016b).
I'm not 100% convinced that this is always working as desired, since in
some places w32api includes are done using <w32api/something.h>, which
will find them via the path /usr/include.
If this does turn out to be needed, this could also be implemented by
constructing the appropriate compiler flags once, rather than on every
compiler invocation.
b55e3f1916