[libc] fixup nascent pthread_condattr_test (#89308)

- use namespaced identifiers
- add corresponding headers for namespaced declarations
- replace time.h and errno.h with finer grain includes
- update cmake

Fixes: #88987
Fixes: #89261
Link: #88997
Link: #89262
GitOrigin-RevId: 854cc8986650267846c5eaf8ba164584a9ea7c01
2 files changed