cross-GDC for tiny embedded Linux

[Dmitry Ponyatov]

> Here the next problem of building `gcc-12.3.0` with 
> `uClibc-ng-1.0.44` (i386 target):

fixed by moving to `musl` usage -- not a surprise that `uClibc` 
becomes obsoleted libc comparing their compilation time, 
configuration complexity, and incompatibility with modern 
toolchains

But the next linking error, what is going to be?

```
/home/ponyatov/player/host/lib/gcc/i686-linux-musl/12.3.0/../../../../i686-linux-musl/bin/ld: /home/ponyatov/player/host/lib/gcc/i686-linux-musl/12.3.0/../../../../i686-linux-musl/lib/libgphobos.a(os.o): in function `_D4core8internal2gc2os10os_mem_mapFNbNikbZPv':
/home/ponyatov/player/ref/gcc-12.3.0/libphobos/libdruntime/core/internal/gc/os.d:145:(.text._D4core8internal2gc2os10os_mem_mapFNbNikbZPv+0x22): undefined reference to `mmap64'
/home/ponyatov/player/host/lib/gcc/i686-linux-musl/12.3.0/../../../../i686-linux-musl/bin/ld: /home/ponyatov/player/host/lib/gcc/i686-linux-musl/12.3.0/../../../../i686-linux-musl/lib/libgphobos.a(fiber.o):/home/ponyatov/player/ref/gcc-12.3.0/libphobos/libdruntime/core/thread/fiber.d:1050: more undefined references to `mmap64' follow
collect2: error: ld returned 1 exit status
```