use __attribute__((const)) for errno and pthread_self if __GNUC__ is defined
[musl] / crt /
drwxr-xr-x   ..
-rw-r--r-- 0 crt1.c
-rw-r--r-- 0 crti.c
-rw-r--r-- 0 crtn.c
drwxr-xr-x - i386
drwxr-xr-x - x86_64