all: bare metal support (fix -freestanding) (#9624)

vlib/builtin/linux_bare/old/mm_bare.v

@@ -0,0 +1,58 @@
+module builtin
+
+const (
+	mem_prot  = Mm_prot(int(Mm_prot.prot_read) | int(Mm_prot.prot_write))
+	mem_flags = Map_flags(int(Map_flags.map_private) | int(Map_flags.map_anonymous))
+	page_size = u64(Linux_mem.page_size)
+)
+
+pub fn mm_pages(size u64) u32 {
+	pages := (size + u64(4) + page_size) / page_size
+	return u32(pages)
+}
+
+pub fn mm_alloc(size u64) (&byte, Errno) {
+	pages := mm_pages(size)
+	n_bytes := u64(pages * u32(Linux_mem.page_size))
+
+	a, e := sys_mmap(0, n_bytes, mem_prot, mem_flags, -1, 0)
+	if e == .enoerror {
+		mut ap := &int(a)
+		*ap = pages
+		return &byte(a + 4), e
+	}
+	return &byte(0), e
+}
+
+pub fn mm_free(addr &byte) Errno {
+	ap := &int(addr - 4)
+	size := u64(*ap) * u64(Linux_mem.page_size)
+
+	return sys_munmap(ap, size)
+}
+
+pub fn mem_copy(dest0 voidptr, src0 voidptr, n int) voidptr {
+	mut dest := &byte(dest0)
+	src := &byte(src0)
+	for i in 0 .. n {
+		dest[i] = src[i]
+	}
+	return dest0
+}
+
+[unsafe]
+pub fn malloc(n int) &byte {
+	if n < 0 {
+		panic('malloc(<0)')
+	}
+
+	ptr, e := mm_alloc(u64(n))
+	assert e == .enoerror
+	assert !isnil(ptr)
+	return ptr
+}
+
+[unsafe]
+pub fn free(ptr voidptr) {
+	assert mm_free(ptr) == .enoerror
+}