IMHO the only practical solution to this problem is to compile and test the code at least on the popular compilers (e.g. GCC, Clang and MSVC), which is quite easy today with CI services like GH Actions.
The standard also often doesn't tell what features are actually supported by different compilers (e.g. MSVC famously will never be C99 compliant, but eventually - really soon now! - C11 compliant) - so the language standard is in reality more like a recommendation of what features are more likely to work across compilers than others.
Finally, even standard compliant code may still trigger a lot of warnings, and those warnings are different on different compilers or different versions of the same compiler, so testing on different compilers is needed anyway to cleanup warnings.
It's not an either-or. Write standard-compliant code as much as possible, and test it with real-world compilers (and work around their quirks or limitations if needed). Somebody trying to compile it 20 years later will thank you.
The standard also often doesn't tell what features are actually supported by different compilers (e.g. MSVC famously will never be C99 compliant, but eventually - really soon now! - C11 compliant) - so the language standard is in reality more like a recommendation of what features are more likely to work across compilers than others.
Finally, even standard compliant code may still trigger a lot of warnings, and those warnings are different on different compilers or different versions of the same compiler, so testing on different compilers is needed anyway to cleanup warnings.