To support building out-of-tree kernel modules, the source tree prefix
is attempted to be stripped from change object file paths to make them
relative. However, if the path is already relative, the change can
strip a substring instead, resulting in build errors.
Ensure just the prefix is stripped instead of any substring.
Fixes: #1282
Fixes: 51a8fad34f ("Add support for building out-of-tree modules")
Add support for clang-built kernels. This is completely automatic, we
check if the kernel was built with clang by looking for
CONFIG_CC_IS_CLANG in config.
This has almost no effect on non-clang built kernels with one exception:
we now do compliler checks _after_ we download kernel sources which is a
waste of resources in case when compilers don't match.
Signed-off-by: Artem Savkov <asavkov@redhat.com>
