No need for -g or -O in LDFLAGS

Fix a mistake in the previous commit.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/Makefile b/Makefile
index 5e0275a..7aa7bce 100644
--- a/Makefile
+++ b/Makefile
@@ -101,7 +101,7 @@
 
 ifndef WINDOWS
 # Note: for coverage testing, build with:
-#     make CFLAGS='--coverage -g3 -O0' LDFLAGS='--coverage -g3 -O0'
+#     make CFLAGS='--coverage -g3 -O0' LDFLAGS='--coverage'
 # For the reference coverage measurement, see tests/scripts/basic-build-test.sh
 covtest:
 	$(MAKE) check