Replace calls to getvar function recently removed

Signed-off-by: Nicolas Thill <nico@openwrt.org>

This mostly helps to avoid confusion when modules are cross-compiled.
Otherwise build folders are named with the host's platform name.

Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>

Tells the host Python to use the target's linker.

Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>

The target's PYTHON3_INC_DIR should take precedence over the host's
include dir when cross-compiling.

Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>

Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>

Required when IPv6 support gets enabled.

Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>

Seems that this allows some goofs, because some files
silently do not get copied and the build succeeds, even though
it shouldn't.

Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>

Seems that if you add a package folder this would also
include the compiled python3 files which increases fw size.

Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>

Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>