package/libnpth: fix musl build

Fix the following musl build failure raised since bump to version 1.7 in
commit 3ef4d24192b20bd1eb5e34c9fa2a6aa5bde91f91 and
https://git.gnupg.org/cgi-bin/gitweb.cgi?p=npth.git;a=commit;h=575573b5b63e147b1906240f192dbe37a26ca4b9:

npth.c:392:21: error: unknown type name 'npth_rwlock_t'; did you mean 'npth_cond_t'?
  392 | npth_rwlock_rdlock (npth_rwlock_t *rwlock)
      |                     ^~~~~~~~~~~~~
      |                     npth_cond_t

Fixes: 3ef4d24192b20bd1eb5e34c9fa2a6aa5bde91f91
 - http://autobuild.buildroot.org/results/d986ba27b734679fd70b4e0f23278ebd38e13c5d

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
2 files changed