You can test raid6 library code from user-space, like this:

  $ cd lib/raid6/test
  $ make

The command in $(shell ...) function is evaluated by /bin/sh by default.
(or, you can change the default shell by setting 'SHELL' in Makefile)

Currently '>&/dev/null' is used to sink both stdout and stderr. Because
this code is bash-ism, it only works when /bin/sh is a symbolic link to
bash (this is the case on RHEL etc.)

This does not work on Ubuntu where /bin/sh is a symbolic link to dash.

I see lots of

  /bin/sh: 1: Syntax error: Bad fd number

and

  warning "your version of binutils lacks ... support"

Replace it with portable '>/dev/null 2>&1'.

Fixes: 4f8c55c5ad49 ("lib/raid6: build proper files on corresponding arch")
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: H. Peter Anvin (Intel) <hpa@zytor.com>
---

 lib/raid6/test/Makefile | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/lib/raid6/test/Makefile b/lib/raid6/test/Makefile
index 3ab8720aa2f8..b9e6c3648be1 100644
--- a/lib/raid6/test/Makefile
+++ b/lib/raid6/test/Makefile

@@ -35,13 +35,13 @@ endif
 ifeq ($(IS_X86),yes)
         OBJS   += mmx.o sse1.o sse2.o avx2.o recov_ssse3.o recov_avx2.o avx512.o recov_avx512.o
         CFLAGS += $(shell echo "pshufb %xmm0, %xmm0" |         \
-                    gcc -c -x assembler - >&/dev/null &&       \
+                    gcc -c -x assembler - >/dev/null 2>&1 &&   \
                     rm ./-.o && echo -DCONFIG_AS_SSSE3=1)
         CFLAGS += $(shell echo "vpbroadcastb %xmm0, %ymm1" |   \
-                    gcc -c -x assembler - >&/dev/null &&       \
+                    gcc -c -x assembler - >/dev/null 2>&1 &&   \
                     rm ./-.o && echo -DCONFIG_AS_AVX2=1)
        CFLAGS += $(shell echo "vpmovm2b %k1, %zmm5" |          \
-                   gcc -c -x assembler - >&/dev/null &&        \
+                   gcc -c -x assembler - >/dev/null 2>&1 &&    \