selftests/bpf: Correct the INDEX address in vmtest.sh

Migration of vmtest to libbpf/ci will change the address
of INDEX in vmtest.sh, which will cause vmtest.sh to not
work due to the failure of rootfs fetching.
Signed-off-by: Pu Lehui <pulehui@huawei.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Tested-by: Lorenzo Fontana <lorenzo.fontana@elastic.co>
Link: https://lore.kernel.org/bpf/20211220050803.2670677-1-pulehui@huawei.com

tools/testing/selftests/bpf/vmtest.sh

@@ -32,7 +32,7 @@ ROOTFS_IMAGE="root.img"
 OUTPUT_DIR="$HOME/.bpf_selftests"
 KCONFIG_URL="https://raw.githubusercontent.com/libbpf/libbpf/master/travis-ci/vmtest/configs/config-latest.${ARCH}"
 KCONFIG_API_URL="https://api.github.com/repos/libbpf/libbpf/contents/travis-ci/vmtest/configs/config-latest.${ARCH}"
-INDEX_URL="https://raw.githubusercontent.com/libbpf/libbpf/master/travis-ci/vmtest/configs/INDEX"
+INDEX_URL="https://raw.githubusercontent.com/libbpf/ci/master/INDEX"
 NUM_COMPILE_JOBS="$(nproc)"
 LOG_FILE_BASE="$(date +"bpf_selftests.%Y-%m-%d_%H-%M-%S")"
 LOG_FILE="${LOG_FILE_BASE}.log"