[source] perf: fix build with kernel 4.9

[LEDE Commits]

mkresin pushed a commit to source.git, branch master:
https://git.lede-project.org/66146a223e78b03388ebb308a0e93503b3216384

commit 66146a223e78b03388ebb308a0e93503b3216384
Author: Mathias Kresin <dev at kresin.me>
AuthorDate: Fri Mar 17 08:29:42 2017 +0100

    perf: fix build with kernel 4.9
    
    The musl workaround isn't required anymore and causes build errors with
    kernel 4.9 when applied.
    
    Signed-off-by: Mathias Kresin <dev at kresin.me>
---
 package/devel/perf/Makefile | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/package/devel/perf/Makefile b/package/devel/perf/Makefile
index f2f8d6c..a9e11b4 100644
--- a/package/devel/perf/Makefile
+++ b/package/devel/perf/Makefile
@@ -61,9 +61,11 @@ MAKE_FLAGS = \
 	WERROR=0 \
 	prefix=/usr
 
+ifdef CONFIG_LINUX_4_4
 ifdef CONFIG_USE_MUSL
  MAKE_FLAGS += EXTRA_CFLAGS="-I$(CURDIR)/musl-include -include $(CURDIR)/musl-compat.h -D__UCLIBC__"
 endif
+endif
 
 define Build/Compile
 	+$(MAKE_FLAGS) $(MAKE) $(PKG_JOBS) \