feat: native GCC - cc1, cc1plus and the gcc driver run on MontaukOS

Cross-build GCC 14.2.0 with --host=x86_64-montauk: the driver, cc1,
cc1plus and collect2 now link as static Montauk ET_EXEC binaries
against the hosted libstdc++, and ship in the SDK. Together with the
native binutils, TCC and the target sysroot, MontaukOS carries a
complete self-contained C and C++ toolchain at 0:/sdk.

libc: anonymous mmap/munmap over SYS_ALLOC (GCC's page allocator
wants mmap; SYS_ALLOC memory is page-aligned by construction),
getpagesize, minimal sysconf, MB_CUR_MAX, isascii/toascii, POSIX id
typedefs (ino_t, dev_t, nlink_t, ...), struct stat fields switched to
proper POSIX types (st_size is a signed off_t now), and a
conventional _STDIO_H guard marker so GMP's FILE detection works.

Build recipe and the five host-build gotchas (bundled config.subs,
gettext removal, stdio guard sniffing, endianness cache preset,
sysroot sdk symlink) are documented in toolchain/README.md. The
devkit stages the driver as gcc.elf/g++.elf/cpp.elf, the backends in
the libexec layout the driver expects, a copy of ld where collect2
searches, and a 0:/tmp scratch dir. Ramdisk: 1604 files, 368 MB.

Co-Authored-By: Claude Fable 5 <[email protected]>

programs/include/libc/sys/mman.h

@@ -0,0 +1,41 @@
+#ifndef _LIBC_SYS_MMAN_H
+#define _LIBC_SYS_MMAN_H
+
+#pragma once
+
+#include <sys/types.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*
+    * Anonymous-memory mmap over SYS_ALLOC. SYS_ALLOC returns
+    * page-aligned process memory, which is exactly what callers like
+    * GCC's page allocator need. File-backed mappings are not
+    * supported and fail with ENODEV.
+*/
+
+#define PROT_NONE  0
+#define PROT_READ  1
+#define PROT_WRITE 2
+#define PROT_EXEC  4
+
+#define MAP_SHARED    0x01
+#define MAP_PRIVATE   0x02
+#define MAP_FIXED     0x10
+#define MAP_ANONYMOUS 0x20
+#define MAP_ANON      MAP_ANONYMOUS
+
+#define MAP_FAILED ((void *)-1)
+
+void *mmap(void *addr, size_t length, int prot, int flags, int fd,
+           long offset);
+int   munmap(void *addr, size_t length);
+int   mprotect(void *addr, size_t length, int prot);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _LIBC_SYS_MMAN_H */