fix clang CFLAGS checks and silence unused argument warnings
diff --git a/configure b/configure
index c2db298..539c9fc 100755
--- a/configure
+++ b/configure
@@ -249,6 +249,7 @@
#
tryflag CFLAGS_TRY -Werror=unknown-warning-option
tryflag CFLAGS_TRY -Werror=unused-command-line-argument
+tryflag CFLAGS_TRY -Werror=ignored-optimization-argument
tryldflag LDFLAGS_TRY -Werror=unknown-warning-option
tryldflag LDFLAGS_TRY -Werror=unused-command-line-argument
@@ -504,6 +505,13 @@
tryflag CFLAGS_AUTO -Werror=pointer-sign
tryflag CFLAGS_AUTO -Werror=pointer-arith
+#
+# GCC ignores unused arguements by default, but Clang needs this extra
+# parameter to stop printing warnings about LDFLAGS passed during
+# compiling stage and CFLAGS passed during linking stage.
+#
+tryflag CFLAGS_AUTO -Qunused-arguments
+
if test "x$warnings" = xyes ; then
tryflag CFLAGS_AUTO -Wall
tryflag CFLAGS_AUTO -Wno-parentheses