runtime symbol lookup error for __attribute__((cold)) functions in dav1d after #451 and -fvisibility=hidden

[kkysen]

After #451, __attribute__((cold)) functions are failing to be resolved at runtime with a symbol lookup error:

> ../dav1d-ia2/build/tools/dav1d -h
../dav1d-ia2/build/tools/dav1d: symbol lookup error: /home/kkysen/work/rust/dav1d-ia2/build/tools/../src/libcallgates.so: undefined symbol: dav1d_num_logical_processors

I say __attribute__((cold)) because all of the functions this happened with were marked as such, but removing the __attribute__((cold)) did not fix the issue. Neither did __attribute__((used)). But __attribute__((visibility("default")) did fix the issue (note that -fvisibility=hidden was set). I'm not really sure what's happening here.

For dav1d specifically, the functions were:

• dav1d_num_logical_processors
• dav1d_init_cpu
• dav1d_get_cpu_flags_x86