compilation error when compiling casbin lib

Hi All,

I am trying to build the project and getting compilation error:

```
# create build directory
oem@maxim:~/work/casbin-CMake-setup$ mkdir build
oem@maxim:~/work/casbin-CMake-setup$ cd build/

# generate makefiles
oem@maxim:~/work/casbin-CMake-setup/build$ cmake ..
-- The CXX compiler identification is GNU 9.3.0
-- The C compiler identification is GNU 9.3.0
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /usr/bin/cc - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Configuring done
-- Generating done
-- Build files have been written to: /home/oem/work/casbin-CMake-setup/build

# build makefiles
oem@maxim:~/work/casbin-CMake-setup/build$ make CasbinClientTest
[ 1%] Building CXX object _deps/casbin-build/casbin/CMakeFiles/casbin.dir/cmake_pch.hxx.gch
[ 3%] Building CXX object _deps/casbin-build/casbin/CMakeFiles/casbin.dir/abac_data.cpp.o
[ 5%] Building CXX object _deps/casbin-build/casbin/CMakeFiles/casbin.dir/enforcer.cpp.o
[ 6%] Building CXX object _deps/casbin-build/casbin/CMakeFiles/casbin.dir/enforcer_cached.cpp.o
[ 8%] Building CXX object _deps/casbin-build/casbin/CMakeFiles/casbin.dir/enforcer_synced.cpp.o
[ 10%] Building CXX object _deps/casbin-build/casbin/CMakeFiles/casbin.dir/internal_api.cpp.o
[ 12%] Building CXX object _deps/casbin-build/casbin/CMakeFiles/casbin.dir/logger.cpp.o
[ 13%] Building CXX object _deps/casbin-build/casbin/CMakeFiles/casbin.dir/management_api.cpp.o
[ 15%] Building CXX object _deps/casbin-build/casbin/CMakeFiles/casbin.dir/pch.cpp.o
[ 17%] Building CXX object _deps/casbin-build/casbin/CMakeFiles/casbin.dir/rbac_api.cpp.o
[ 18%] Building CXX object _deps/casbin-build/casbin/CMakeFiles/casbin.dir/rbac_api_with_domains.cpp.o
[ 20%] Building CXX object _deps/casbin-build/casbin/CMakeFiles/casbin.dir/config/config.cpp.o
/home/oem/work/casbin-CMake-setup/build/_deps/casbin-src/casbin/config/config.cpp:17:10: fatal error: pch.h: No such file or directory
17 | #include "pch.h"
| ^~~~~~~
compilation terminated.
make[3]: *** [_deps/casbin-build/casbin/CMakeFiles/casbin.dir/build.make:253: _deps/casbin-build/casbin/CMakeFiles/casbin.dir/config/config.cpp.o] Error 1
make[2]: *** [CMakeFiles/Makefile2:141: _deps/casbin-build/casbin/CMakeFiles/casbin.dir/all] Error 2
make[1]: *** [CMakeFiles/Makefile2:122: CMakeFiles/CasbinClientTest.dir/rule] Error 2
make: *** [Makefile:169: CasbinClientTest] Error 2
```

Can I get help with this issue? What I am doing wrong? Unfortunately I did not find "official" instructions to build.

Bắt đầu bằng cách tái hiện các lệnh đã được báo cáo trong một thư mục build sạch: chạy `cmake ..` và `make CasbinClientTest`. Kiểm tra cấu hình build xung quanh `_deps/casbin-src/casbin/config/config.cpp` và `pch.h` bị thiếu; được xem là hoàn tất khi target biên dịch thành công và dự án có hướng dẫn build rõ ràng.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.