move definition of the INPUT_FOLDER variable from header to implementation file

unittest/force-styles/test_main.h

@@ -20,6 +20,7 @@
 extern TestConfig test_config;
 extern bool print_stats;
 extern bool verbose;
+extern std::string INPUT_FOLDER;
 
 #define EXPECT_FP_LE_WITH_EPS(val1,val2,eps)                \
     do {                                                    \
@@ -32,12 +33,6 @@ extern bool verbose;
 
 #endif
 
-#define STRINGIFY(val) XSTR(val)
-#define XSTR(val) #val
-static const std::string INPUT_FOLDER = STRINGIFY(TEST_INPUT_FOLDER);
-#undef STRINGIFY
-#undef XSTR
-
 #if defined _WIN32
 static const char PATH_SEP = '\\';
 #else