[PATCH dwarves] Add missing lib/include/bpf -> ../bpf/src symlink

[Luca Boccassi <bluca@debian.org>]

The original "libbpf: allow to use packaged version" had a symlink
as suggested during review:

https://www.spinics.net/lists/dwarves/msg00738.html

git show 82749180b23d3c9c060108bc290ae26507fc324e -- lib/include
commit 82749180b23d3c9c060108bc290ae26507fc324e
Author: Luca Boccassi <bluca@debian.org>
Date:   Mon Jan 4 22:16:22 2021 +0000

    libbpf: allow to use packaged version

    Add a new CMake option, LIBBPF_EMBEDDED, to switch between the
    embedded version and the system version (searched via pkg-config)
    of libbpf. Set the embedded version as the default.

    Signed-off-by: Luca Boccassi <bluca@debian.org>
    Cc: dwarves@vger.kernel.org
    Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/lib/include/bpf b/lib/include/bpf
new file mode 120000
index 0000000..4c41b71
--- /dev/null
+++ b/lib/include/bpf
@@ -0,0 +1 @@
+../bpf/src
\ No newline at end of file

This patch was reverted, and then re-added manually.
But the re-add dropped the symlink, which causes the system bpf/btf.h
to be picked up instead of the local one. Re-add it.

Signed-off-by: Luca Boccassi <bluca@debian.org>
---
 lib/include/bpf | 1 +
 1 file changed, 1 insertion(+)
 create mode 120000 lib/include/bpf

diff --git a/lib/include/bpf b/lib/include/bpf
new file mode 120000
index 0000000..4c41b71
--- /dev/null
+++ b/lib/include/bpf
@@ -0,0 +1 @@
+../bpf/src
\ No newline at end of file
-- 
2.30.2