This should be input in command line?
CXXFLAGS="-fPIC -std=c++17 -nostdinc++ -I/home/igor/Documents/Repos/UnrealEngine/UnrealEngine/Engine/Source/ThirdParty/Unix/LibCxx/include -I/home/igor/Documents/Repos/UnrealEngine/UnrealEngine/Engine/Source/ThirdParty/Unix/LibCxx/include/c++/v1 -stdlib=libc++ -L/home/igor/Documents/Repos/UnrealEngine/UnrealEngine/Engine/Source/ThirdParty/Unix/LibCxx/lib/Unix/x86_64-unknown-linux-gnu/ -L/home/igor/Documents/Repos/UnrealEngine/UnrealEngine/Engine/Source/ThirdParty/Unix/LibCxx/lib/Unix/x86_64-unknown-linux-gnu/libc++.a -L/home/igor/Documents/Repos/UnrealEngine/UnrealEngine/Engine/Source/ThirdParty/Unix/LibCxx/lib/Unix/x86_64-unknown-linux-gnu/libc++abi.a -lm -lc -lgcc_s -lgcc
"
And run cmake, and make, I got compiling error…