Fixed cppcheck / iwyu macros

The macros had not been updated to use given macro arguments as
arguments to the application call, and instead still had an older
variable in it's place.

Rather, it now properly uses $ARGN, which will just copy all given macro
arguments and give it to the called program.

tools.cmake

@@ -1,5 +1,5 @@
 #
-# Copyright (C) 2018 by George Cave - [email protected]
+# Copyright (C) 2018-2020 by George Cave - [email protected]
 #
 # Licensed under the Apache License, Version 2.0 (the "License"); you may not
 # use this file except in compliance with the License. You may obtain a copy of
@@ -29,15 +29,15 @@ endmacro()
 # used as the options set.
 macro(include_what_you_use)
   if(IWYU AND IWYU_EXE)
-    set(CMAKE_CXX_INCLUDE_WHAT_YOU_USE "${IWYU_EXE};${IWYU_STRING}")
+    set(CMAKE_CXX_INCLUDE_WHAT_YOU_USE ${IWYU_EXE} ${ARGN})
   endif()
 endmacro()
 
 # Adds cppcheck to the compilation, with the given arguments being used as the
 # options set.
 macro(cppcheck)
   if(CPPCHECK AND CPPCHECK_EXE)
-    set(CMAKE_CXX_CPPCHECK "${CPPCHECK_EXE};${CPPCHECK_STRING}")
+    set(CMAKE_CXX_CPPCHECK ${CPPCHECK_EXE} ${ARGN})
   endif()
 endmacro()