Mac M2 Monterey proc_pid_rusage 问题

**Describe the bug (描述bug)**

下载apache-brpc-1.5.0-src.tar.gz 编译运行，运行时抛出报警

W0522 13:33:41 259 src/bvar/default_variables.cpp:452] Fail to proc_pid_rusage: Invalid argument

**To Reproduce (复现方法)**

**Expected behavior (期望行为)**

**Versions (各种版本)**
OS: Mac M2 Monterey
Compiler:
brpc: 1.5.0
protobuf: libprotoc 3.21.12

**Additional context/screenshots (更多上下文/截图)**

Start by reading src/bvar/default_variables.cpp around line 452 and trace the proc_pid_rusage call on Mac M2 Monterey. Reproduce the warning with brpc 1.5.0, then verify the resource-usage path no longer reports Invalid argument on that environment.

Written by the indexing model from the issue text.