cmake clang/compiler_flags.cmake: Re-enable Wunused-function for clang

All warnings in the code base have been resolved.

Signed-off-by: Tom Hughes <[email protected]>

Author: thughes

cmake/compiler/clang/compiler_flags.cmake

@@ -103,7 +103,6 @@ check_set_compiler_property(PROPERTY warning_extended
                             #FIXME: need to fix all of those
                             -Wno-self-assign
                             -Wno-address-of-packed-member
-                            -Wno-unused-function
                             -Wno-initializer-overrides
                             -Wno-section
                             -Wno-unused-variable