809216233555 ("selftests/harness: remove use of LINE_MAX") introduced
asprintf into kselftest_harness.h, which is a GNU extension and needs
_GNU_SOURCE to either be defined prior to including headers or with the
-D_GNU_SOURCE flag passed to the compiler.

Fixes: 809216233555 ("selftests/harness: remove use of LINE_MAX")
Signed-off-by: Edward Liaw <edliaw@google.com>
---
 tools/testing/selftests/rtc/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/rtc/Makefile b/tools/testing/selftests/rtc/Makefile
index 55198ecc04db..4ef7ee969003 100644
--- a/tools/testing/selftests/rtc/Makefile
+++ b/tools/testing/selftests/rtc/Makefile
@@ -1,5 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0
-CFLAGS += -O3 -Wl,-no-as-needed -Wall
+CFLAGS += -O3 -Wl,-no-as-needed -Wall -D_GNU_SOURCE
 LDLIBS += -lrt -lpthread -lm

 TEST_GEN_PROGS = rtctest
--
2.45.0.rc0.197.gbae5840b3b-goog