vfio: selftests: Fix out-of-tree build with make O=

The test programs are compiled via a static pattern rule that requires
intermediate .o files:

  $(TEST_GEN_PROGS): %: %.o $(LIBVFIO_O)

After lib.mk prefixes TEST_GEN_PROGS with $(OUTPUT), this creates
dependencies on .o files in the output directory (e.g.
$(OUTPUT)/vfio_dma_mapping_test.o). However, there is no rule to compile
these .o files from the source directory .c files when OUTPUT differs
from the source directory.

Add an explicit chain of pattern rules:
  $(OUTPUT)/% -> $(OUTPUT)/%.o -> %.c

Following the same pattern already used in libvfio.mk for the library
objects.

Fixes: 19faf6fd969c ("vfio: selftests: Add a helper library for VFIO selftests")
Reviewed-by: David Matlack <dmatlack@google.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/0-v2-4ccc247e6aff+1d93-vfio_st_make_o_jgg@nvidia.com
Signed-off-by: Alex Williamson <alex@shazbot.org>

0 files changed, 0 insertions, 0 deletions