As a result of previous commits, ethtool source now builds with gcc
versions 7-11 without any compiler warning with "-Wall -Wextra". Add
"-Wextra" to default cflags to make sure that any new warnings are
caught as early as possible.

Suggested-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Michal Kubecek <redacted>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
---
 Makefile.am | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Makefile.am b/Makefile.am
index 38dde098c1e6..aca0ad7bc773 100644
--- a/Makefile.am
+++ b/Makefile.am

@@ -1,4 +1,4 @@
-AM_CFLAGS = -Wall
+AM_CFLAGS = -Wall -Wextra
 AM_CPPFLAGS = -I$(top_srcdir)/uapi
 LDADD = -lm
 

-- 
2.28.0