[klibc] Makefile: Honour KBUILD_SRC variable

Currently it's necessary to specify both KBUILD_SRC and srctree to
make everything work properly in an out-of-tree build.  It should
only be necessary to specify KBUILD_SRC.  Initialise srctree
accordingly.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
1 file changed