chromium: libsync includes the nonexistant `sys/cdefs.h` in musl

[concatime]

Hi, when building Chromium v94.0.4606.61, I get:

In file included from ../chromium-94.0.4606.61/third_party/libsync/src/sync.c:30:
../chromium-94.0.4606.61/third_party/libsync/src/include/sync/sync.h:22:10: fatal error: 'sys/cdefs.h' file not found
#include <sys/cdefs.h>
         ^~~~~~~~~~~~~

Shouldn’t there be a patch for libsync in the musl directory too ?

Also... thank you for the awesomeness of this project, very helpful!