On Ubuntu 20.04, devtool cannot be used in recipe inheriting
python3native. Unexport _PYTHON_SYSCONFIGDATA_NAME as a workaround.
To check if it can be revert with next bitbake releases.
Signed-off-by: Lionel VITTE <lionel.vitte@st.com>
Change-Id: I7d73d05e1a5d58dedf69b3aefb3e07c35b92800d