[PATCH v3 bpf-next 13/14] samples: bpf: makefile: add sysroot support

[Ivan Khoronzhuk]

Basically it only enables that was added by previous couple fixes.
Sysroot contains correct libs installed and its headers ofc. Useful
when working with NFC or virtual machine.

Usage:

clean (on demand)
    make ARCH=arm -C samples/bpf clean
    make ARCH=arm -C tools clean
    make ARCH=arm clean

configure and install headers:

    make ARCH=arm defconfig
    make ARCH=arm headers_install

build samples/bpf:
    make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- samples/bpf/ \
    SYSROOT="path/to/sysroot"

Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@xxxxxxxxxx>
---
 samples/bpf/Makefile | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index 133123d4c7d7..57ddf055d6c3 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -194,6 +194,11 @@ TPROGS_CFLAGS += -I$(srctree)/tools/lib/
 TPROGS_CFLAGS += -I$(srctree)/tools/include
 TPROGS_CFLAGS += -I$(srctree)/tools/perf
 
+ifdef SYSROOT
+TPROGS_CFLAGS += --sysroot=${SYSROOT}
+TPROGS_LDFLAGS := -L${SYSROOT}/usr/lib
+endif
+
 EXTRA_CXXFLAGS := $(TPROGS_CFLAGS)
 
 # options not valid for C++
-- 
2.17.1