Currently we check for OS before using PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP but it would be better to check for it being defined rather.
This helps in fixing build with musl on linux where PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP is not available but its running on Linux. Current assumption is that its universally available on Linux based OSes
Diff:
Fixed in revision 7732.
Attached commited patch to the bug.