BUILD: Don't abort on unknown clang option (for options available on latter...

BUILD: Don't abort on unknown clang option (for options available on latter versions, but CI is using an older one)

CMakeLists.txt

@@ -44,6 +44,7 @@ set(clang_C_FLAGS
     -Wno-extra-semi
     -Wno-format-nonliteral
     -Wno-missing-variable-declarations
+    -Wno-unknown-warning-option
 )
 
 # Find dependencies