Disable nodiscard attribute when compiling with Clang.
Clang raised errors with this attributes placement.
Clang will use __attribute__((warn_unused_result)) instead which it seems
to be fine with.
Fixes
@@ -198,7 +198,7 @@ TCODLIB_CAPI int TCOD_strncasecmp(const char *s1, const char *s2, size_t n);
#define TCODLIB_FORMAT(str_index, first_arg)
#endif
-#if defined(__cplusplus) && __cplusplus >= 201703L
+#if defined(__cplusplus) && __cplusplus >= 201703L && !defined(__clang__)
#define TCOD_NODISCARD [[nodiscard]]
#elif defined(_MSC_VER)
#define TCOD_NODISCARD _Check_return_
