[PATCH bpf-next v2] bpftool: fix profiler build on systems without /usr/include/asm symlink

[Tobias Klauser <tklauser@distanz.ch>]

When compiling bpftool on a system where the /usr/include/asm symlink
doesn't exist (e.g. on an Ubuntu system without gcc-multilib installed),
the build fails with:

    CLANG    skeleton/profiler.bpf.o
  In file included from skeleton/profiler.bpf.c:4:
  In file included from /usr/include/linux/bpf.h:11:
  /usr/include/linux/types.h:5:10: fatal error: 'asm/types.h' file not found
  #include <asm/types.h>
           ^~~~~~~~~~~~~
  1 error generated.
  make: *** [Makefile:123: skeleton/profiler.bpf.o] Error 1

In certain cases (e.g. for container builds), installing gcc-multilib
and all its dependencies - which are otherwise not needed to build
bpftool - unnecessarily increases the image size.

Thus, fix this by adding /usr/include/$(uname -m)-linux-gnu to the
clang search path so <asm/types.h> can be found.

Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
---
 tools/bpf/bpftool/Makefile | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
index 20a90d8450f8..db54e9bb873a 100644
--- a/tools/bpf/bpftool/Makefile
+++ b/tools/bpf/bpftool/Makefile
@@ -120,7 +120,8 @@ $(OUTPUT)_bpftool: $(_OBJS) $(LIBBPF)
 	$(QUIET_LINK)$(CC) $(CFLAGS) $(LDFLAGS) -o $@ $(_OBJS) $(LIBS)
 
 skeleton/profiler.bpf.o: skeleton/profiler.bpf.c
-	$(QUIET_CLANG)$(CLANG) -I$(srctree)/tools/lib -g -O2 -target bpf -c $< -o $@
+	$(QUIET_CLANG)$(CLANG) -I/usr/include/$(shell uname -m)-linux-gnu \
+		-I$(srctree)/tools/lib -g -O2 -target bpf -c $< -o $@
 
 profiler.skel.h: $(OUTPUT)_bpftool skeleton/profiler.bpf.o
 	$(QUIET_GEN)$(OUTPUT)./_bpftool gen skeleton skeleton/profiler.bpf.o > $@
-- 
2.25.1