What strikes me as weird is that I know of exactly one
compiler system that got it right (...) Turbo Pascal.
Long Live Turbo Pascal.
when you cannot (...) CPP
I really see no way forward to be able to modernize CPP build systems. CPP has invented it's own paradigm for how a build system should work. Unless square 1 is "support CPP" making something support cpp is almost impossible.
cpp(1) is not where the paradigm stems from, the same paradigm was there before and was there even before C itself. The whole idea of preprocessor stems from assembly programming and the idea that having one file with lines like "PORTB .equ 0x17" and reusing it is useful, in the same spirit the way how ld(1) works was/is useful for assembly programming (you can jump arbitrarily between notionally different functions, and in fact GCC is perfectly capable of generating object files that do that from C/C++ code). On the other hand, cpp(1) is useful for more things than just C/C++, there are even programs which read their configuration by means of popen("cpp /etc/foo").
And as for supporting ld(1) and unix toolchain in general, see my remark above about how FPC works, IIRC MSVC compiller does something similar for C++, albeit in more limited manner (stdaux.h and such stuff).
