Revert "gn_base.bbclass: Make build dir path checking more robust"

This reverts commit 82e0bd85.

The build directory is created in the do_configure task that is executing GN which relies on the build directory check. The os.path.samefile() raises an exception when os.stat() fails and therefore cannot be used to compare paths of non-existing directories.

Signed-off-by: Robert Drab robert.drab@huawei.com