selftests/bpf: Install btf_dump test cases

mainline inclusion
from mainline-5.12-rc1
commit b8d1cbef
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5EUVD
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b8d1cbef2ea4415edcdb5a825972d93b63fcf63c

-------------------------------------------------

The btf_dump test cannot access the original source files for comparison
when running the selftests out of tree, causing several failures:

awk: btf_dump_test_case_syntax.c: No such file or directory
...

Add those files to $(TEST_FILES) to have "make install" pick them up.
Signed-off-by: NJean-Philippe Brucker <jean-philippe@linaro.org>
Signed-off-by: NAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210113163319.1516382-6-jean-philippe@linaro.org
(cherry picked from commit b8d1cbef)
Signed-off-by: NWang Yufen <wangyufen@huawei.com>

Conflicts:
	tools/testing/selftests/bpf/Makefile
Signed-off-by: NWang Yufen <wangyufen@huawei.com>

tools/testing/selftests/bpf/Makefile

@@ -47,6 +47,7 @@ endif
 
 TEST_GEN_FILES = test_lwt_ip_encap.o \
 	test_tc_edt.o
+TEST_FILES = $(wildcard progs/btf_dump_test_case_*.c)
 
 # Order correspond to 'make run_tests' order
 TEST_PROGS := test_kmod.sh \