builtin: use dlmalloc for -freestanding (#13054)

vlib/builtin/linux_bare/memory_managment.v

@@ -1,5 +1,7 @@
 module builtin
 
+import dlmalloc
+
 fn mm_alloc(size u64) (&byte, Errno) {
 	// BEGIN CONSTS
 	// the constants need to be here, since the initialization of other constants,
@@ -27,3 +29,64 @@ fn mm_free(addr &byte) Errno {
 		return sys_munmap(addr - sizeof(u64), size + sizeof(u64))
 	}
 }
+
+fn system_alloc(_ voidptr, size usize) (voidptr, usize, u32) {
+	// BEGIN CONSTS
+	// the constants need to be here, since the initialization of other constants,
+	// which happen before these ones would, require malloc
+	mem_prot := MemProt(int(MemProt.prot_read) | int(MemProt.prot_write))
+	map_flags := MapFlags(int(MapFlags.map_private) | int(MapFlags.map_anonymous))
+	// END CONSTS
+
+	a, e := sys_mmap(&byte(0), u64(size + sizeof(u64)), mem_prot, map_flags, -1, 0)
+
+	if e == .enoerror {
+		return a, size, 0
+	}
+	return voidptr(0), 0, 0
+}
+
+fn system_remap(_ voidptr, ptr voidptr, oldsize usize, newsize usize, can_move bool) voidptr {
+	return voidptr(0)
+}
+
+fn system_free_part(_ voidptr, ptr voidptr, oldsize usize, newsize usize) bool {
+	_, e := sys_mremap(ptr, u64(oldsize), u64(newsize), 0)
+	if e == .enoerror {
+		return true
+	}
+	e2 := sys_munmap(voidptr(usize(ptr) + newsize), u64(oldsize - newsize))
+
+	return e2 == .enoerror
+}
+
+fn system_free(_ voidptr, ptr voidptr, size usize) bool {
+	unsafe {
+		return sys_munmap(ptr, u64(size)) == .enoerror
+	}
+}
+
+fn system_can_release_part(_ voidptr, _ u32) bool {
+	return true
+}
+
+fn system_allocates_zeros(_ voidptr) bool {
+	return true
+}
+
+fn system_page_size(_ voidptr) usize {
+	return 4096
+}
+
+fn get_linux_allocator() dlmalloc.Allocator {
+	return dlmalloc.Allocator{
+		alloc: system_alloc
+		remap: system_remap
+		free_part: system_free_part
+		free_: system_free
+		can_release_part: system_can_release_part
+		allocates_zeros: system_allocates_zeros
+		page_size: system_page_size
+		data: voidptr(0)
+	}
+}