error: cannot initialize return object of type 'uint64_t' (aka 'unsigned long') with an rvalue of type 'pthread_t'

[yurivict]

Describe the bug (描述bug)

/usr/ports/devel/brpc/work/incubator-brpc-1.3.0/src/butil/compat.h:85:12: error: cannot initialize return object of type 'uint64_t' (aka 'unsigned long') with an rvalue of type 'pthread_t' (aka 'pthread *')
    return pthread_self();
           ^~~~~~~~~~~~~~
2 errors generated.
``

**To Reproduce (复现方法)**
build on FreeBSD

According to the documentation pthread_self returns pthread_t:

NAME pthread_self – get the calling thread's ID

LIBRARY POSIX Threads Library (libpthread, -lpthread)

SYNOPSIS

include

 pthread_t
 pthread_self(void);

pthread_t generally can not and should not be typecast to any other type.

**Versions (各种版本)**
OS: FreeBSD 13.1
Compiler: clang-14
brpc: 1.3.0

[wwbmmm]

related: #2072