configure: don't error on unused results

Author: dwfreed

configure.ac

@@ -135,6 +135,7 @@ CFLAGS="-ggdb3 -O2 -fvar-tracking-assignments -fno-omit-frame-pointer \
 	-Wno-unused-parameter -Wno-implicit-fallthrough -Wno-int-in-bool-context \
 	-Wno-format-truncation -Wno-maybe-uninitialized \
 	-Wno-error=deprecated-declarations -Wno-error=stringop-overflow \
+	-Wno-error=unused-result \
 	$CFLAGS"
 
 AC_DEFINE_DIR([PREFIX],[prefix],[Set to prefix.])