tools/bpf: generate pkg-config file for libbpf

Generate a libbpf.pc file at build time so that users can rely
on pkg-config to find the library, its CFLAGS and LDFLAGS.

Signed-off-by: Luca Boccassi <bluca@debian.org>
Acked-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
diff --git a/tools/lib/bpf/.gitignore b/tools/lib/bpf/.gitignore
index 4db7475..7d9e182 100644
--- a/tools/lib/bpf/.gitignore
+++ b/tools/lib/bpf/.gitignore
@@ -1,3 +1,4 @@
 libbpf_version.h
+libbpf.pc
 FEATURE-DUMP.libbpf
 test_libbpf