selftests/bpf: Copy test_kmods when installing selftest

Commit d6212d8 ("selftests/bpf: Consolidate kernel modules into
common directory") consolidated the Makefile of test_kmods. However,
since it removed test_kmods from TEST_GEN_PROGS_EXTENDED, the kernel
modules required by bpf selftests are now missing from kselftest_install
when "make install". Fix it by adding test_kmod to TEST_GEN_FILES.

Fixes: d6212d8 ("selftests/bpf: Consolidate kernel modules into common directory")
Signed-off-by: Amery Hung <[email protected]>
Signed-off-by: Andrii Nakryiko <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]

Author: ameryhung

tools/testing/selftests/bpf/Makefile

@@ -137,7 +137,7 @@ TEST_GEN_PROGS_EXTENDED = \
 	xdping \
 	xskxceiver
 
-TEST_GEN_FILES += liburandom_read.so urandom_read sign-file uprobe_multi
+TEST_GEN_FILES += $(TEST_KMODS) liburandom_read.so urandom_read sign-file uprobe_multi
 
 ifneq ($(V),1)
 submake_extras := feature_display=0