I find both the message displayed on build:

Warning: The hard system call mapping variant is still work in progress.
         Do neither expect it to compile on all platforms (because of
         conflicts with vendor prototypes) nor to actually work!

and the fact that the generated lib doesn't pass its own selftest:

[...]
Initializing Pth system (spawns scheduler and main thread)
*** ERROR, TEST FAILED:
*** errno=1
[...]

somewhat scaring.
I'd feel better if the plain pth and pth-syscall could
coexist on one system.

best regards
Matthias