[PATCH v2 2/2] selftests/mm: suppress compiler error in liburing check

[Li Wang <liwang@redhat.com>]

When building the mm selftests on a system without liburing development
headers, check_config.sh leaks a raw compiler error:

  /tmp/tmp.kIIOIqwe3n.c:2:10: fatal error: liburing.h: No such file or directory
      2 | #include <liburing.h>
        |          ^~~~~~~~~~~~

Since this is an expected failure during the configuration probe,
redirect the compiler output to /dev/null to hide it.

And the build system prints a clear warning when this occurs:

  Warning: missing liburing support. Some tests will be skipped.

Because the user is properly notified about the missing dependency, the
raw compiler error is redundant and only confuse users.

Additionally, update the Makefile to use $(Q) and $(call msg,...) for
the check_config.sh execution. This aligns the probe with standard
kbuild output formatting, providing a clean "CHK" message instead of
printing the raw command during the build.

Signed-off-by: Li Wang <liwang@redhat.com>
---
 tools/testing/selftests/mm/Makefile        | 3 ++-
 tools/testing/selftests/mm/check_config.sh | 2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile
index 3b222cd6a048..2f6d2a207a0c 100644
--- a/tools/testing/selftests/mm/Makefile
+++ b/tools/testing/selftests/mm/Makefile
@@ -262,7 +262,8 @@ $(OUTPUT)/migration: LDLIBS += -lnuma
 $(OUTPUT)/rmap: LDLIBS += -lnuma
 
 local_config.mk local_config.h: check_config.sh
-	CC="$(CC)" CFLAGS="$(CFLAGS)" ./check_config.sh
+	$(call msg,CHK,config,$@)
+	$(Q)CC="$(CC)" CFLAGS="$(CFLAGS)" ./check_config.sh
 
 EXTRA_CLEAN += local_config.mk local_config.h
 
diff --git a/tools/testing/selftests/mm/check_config.sh b/tools/testing/selftests/mm/check_config.sh
index b84c82bbf875..32beaefe279e 100755
--- a/tools/testing/selftests/mm/check_config.sh
+++ b/tools/testing/selftests/mm/check_config.sh
@@ -16,7 +16,7 @@ echo "#include <sys/types.h>"        > $tmpfile_c
 echo "#include <liburing.h>"        >> $tmpfile_c
 echo "int func(void) { return 0; }" >> $tmpfile_c
 
-$CC $CFLAGS -c $tmpfile_c -o $tmpfile_o
+$CC $CFLAGS -c $tmpfile_c -o $tmpfile_o >/dev/null 2>&1
 
 if [ -f $tmpfile_o ]; then
     echo "#define LOCAL_CONFIG_HAVE_LIBURING 1"  > $OUTPUT_H_FILE
-- 
2.53.0