build: shut clang up about unused flags

clang considers use of a flag an error if it's not used.
Strange, but true. Shut it up.

Signed-off-by: Ronald G. Minnich <rminnich@gmail.com>

amd64/include/clang-3.4.json

@@ -1,7 +1,8 @@
 {
 	"buildflags": {
 		"Cflags": [
-				"-mno-implicit-float"
+				"-mno-implicit-float",
+				"-Qunused-arguments"
 			]
 	}
 }

amd64/include/clang-3.5.json

@@ -1,7 +1,8 @@
 {
 	"buildflags": {
 		"Cflags": [
-				"-mno-implicit-float"
+				"-mno-implicit-float",
+				"-Qunused-arguments"
 			]
 	}
 }

amd64/include/clang-3.6.json

@@ -1,7 +1,8 @@
 {
 	"buildflags": {
 		"Cflags": [
-				"-mno-implicit-float"
+				"-mno-implicit-float",
+				"-Qunused-arguments"
 			]
 	}
 }

amd64/include/clang-3.7.json

@@ -1,7 +1,8 @@
 {
 	"buildflags": {
 		"Cflags": [
-				"-mno-implicit-float"
+				"-mno-implicit-float",
+				"-Qunused-arguments"
 			]
 	}
 }

amd64/include/clang-3.8.json

@@ -1,7 +1,8 @@
 {
 	"buildflags": {
 		"Cflags": [
-				"-mno-implicit-float"
+				"-mno-implicit-float",
+				"-Qunused-arguments"
 			]
 	}
 }

amd64/include/clang.json

@@ -1,7 +1,8 @@
 {
 	"buildflags": {
 		"Cflags": [
-				"-mno-implicit-float"
+				"-mno-implicit-float",
+				"-Qunused-arguments"
 			]
 	}
 }