build: fix build fail on clang 15

Fixed pthread-related CMake checks. The checks code is built with
`-pedantic-errors` and it leads to errors of the following kind on
clang 15:

```
<...>/CMakeFiles/CMakeScratch/TryCompile-78KaOK/src.c:4:17: error: a
    function declaration without a prototype is deprecated in all
    versions of C [-Werror,-Wstrict-prototypes]
        int main() { pthread_setname_np(pthread_self(), ""); }
                ^
                 void
```

Fixed a warning in the SQL code (it's an error in Debug build):

```
<...>/src/box/sql/vdbeaux.c:170:13: error: variable 'n' set but not used
    [-Werror,-Wunused-but-set-variable]
        static int n = 0;
```

Fixed several warnings from lemon.c of the following kind:

```
<...>/extra/lemon.c:173:6: warning: a function declaration without a
    prototype is deprecated in all versions of C and is treated as a
    zero-parameter prototype in C2x, conflicting with a subsequent
    definition [-Wdeprecated-non-prototype]
void FindRulePrecedences();
     ^
<...>/extra/lemon.c:766:6: note: conflicting prototype is here
void FindRulePrecedences(struct lemon *xp)
```

See also https://github.com/tarantool/small/issues/57

Fixes #8110

NO_DOC=build fix
NO_TEST=build fix