"Undefined identifier" in the BUILD.gn file

[Điền Đô]

I made the project build with the following process:

gn gen out/libc++ --args="is_debug=true use_custom_libcxx=false use_custom_libcxx_for_host=false"

ninja -C out/libc++

Then,  I got some warnings about using is_pod, as you saw in the picture. And I had build failure.
I also get the suggestion as shown in the Pic,  define _SILENCE_CXX20_IS_POD_DEPRECATION_WARNING or _SILENCE_ALL_CXX20_DEPRECATION_WARNINGS to suppress this warning.

I followed the error message's suggestion but no success :((

I searched on the internet and I found a solution to this problem.
Make changes in the BUILD.gn file adding macro definitions:

D:\Workplace\webrtc-checkout\src\build\config\compiler\BUILD.gn

Add macro definitions:

defines += ["_SILENCE_CXX20_IS_POD_DEPRECATION_WARNING=1","_SILENCE_ALL_CXX20_DEPRECATION_WARNINGS=1"]

I have 2 questions:
1. What to do when making changes in BUILD.gn files to rebuild the library? Looks like I'm missing something.
2. Is there a faster way to get rid of notifications like I originally mentioned?

Thanks for watching:))