<bionic/macros.h>: replace align_up()/align_down() with clang's builtins.

Change-Id: If39cf028e9a22fc2008ee9d1ba683a4d0d038325
diff --git a/libc/bionic/elf_note.cpp b/libc/bionic/elf_note.cpp
index 9cc6b21..efe3844 100644
--- a/libc/bionic/elf_note.cpp
+++ b/libc/bionic/elf_note.cpp
@@ -47,11 +47,11 @@
     const ElfW(Nhdr)* note = reinterpret_cast<const ElfW(Nhdr)*>(p);
     p += sizeof(ElfW(Nhdr));
     const char* name = reinterpret_cast<const char*>(p);
-    if (__builtin_add_overflow(p, align_up(note->n_namesz, 4), &p)) {
+    if (__builtin_add_overflow(p, __builtin_align_up(note->n_namesz, 4), &p)) {
       return false;
     }
     const char* desc = reinterpret_cast<const char*>(p);
-    if (__builtin_add_overflow(p, align_up(note->n_descsz, 4), &p)) {
+    if (__builtin_add_overflow(p, __builtin_align_up(note->n_descsz, 4), &p)) {
       return false;
     }
     if (p > note_end) {