lvmpolld: _strerror_r has return type 'const char *' but returns 'int' with musl libc

[marv]

Building LVM 2.03.16 on a musl-based system I get the following warning:

lvmpolld-core.c: In function '_strerror_r':                                                                                                                               
lvmpolld-core.c:56:16: warning: returning 'int' from a function with return type 'const char *' makes pointer from integer without a cast [-Wint-conversion]              
   56 |         return strerror_r(errnum, data->buf, sizeof(data->buf)); /* never returns NULL */                                                                         
      |                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Recent compilers are getting stricter and with clang-15.0.0 this is now an error

musl declares strerror_r as:

int strerror_r (int, char *, size_t);

while glibc declares it as:

extern char *strerror_r (int __errnum, char *__buf, size_t __buflen)

musl's is compliant with POSIX, which states:

#include <string.h>

char *strerror(int errnum);

int strerror_r(int errnum, char *strerrbuf, size_t buflen);

https://www.unix.com/man-page/posix/3posix/strerror_r/

[zkabelac]

Upstream fix:
https://listman.redhat.com/archives/lvm-devel/2022-November/024479.html