major cleanup of the test folders CMakeLists.txt

The new code does not rely on globally defined include directories
anymore. Additionally a lot of conditional code and has been removed
which improves readability a lot.

test/macro-test.cc

@@ -29,7 +29,7 @@
 #include <gtest/gtest.h>
 
 #define FMT_USE_VARIADIC_TEMPLATES 0
-#include "format.h"
+#include <cppformat/format.h>
 
 #define IDENTITY(x) x