gn2bp: Added required include PATH

When -sysroot=build/linux/debian_bullseye_amd64-sysroot is passed,
build/linux/debian_bullseye_amd64-sysroot/usr/include/x86_64-linux-gnu
also should be in the include path.

Test: ./update_results.sh
Change-Id: I9bdf8d0711bb9f91e118eed8aef8db5c7520126c