refactor(util): remove platform-specific M_FALLTHROUGH_INTENDED defines

src/util/platform.h

@@ -22,19 +22,4 @@
 #error We do not support your compiler. Please email [email protected] and tell us about your use case.
 #endif
 
-#if defined(__clang__) && defined(__has_warning)
-#if __has_feature(cxx_attributes) && __has_warning("-Wimplicit-fallthrough")
-#define M_FALLTHROUGH_INTENDED [[clang::fallthrough]]
-#endif
-#elif defined(__GNUC__) && __GNUC__ >= 7
-// Taken from https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wimplicit-fallthrough_003d
-// We could also use a comment, but that would require ccache users to set the
-// keep_comments_cpp option. If we switch to C++17, we can use [[fallthough]].
-#define M_FALLTHROUGH_INTENDED __attribute__ ((fallthrough));
-#endif
-
-#ifndef M_FALLTHROUGH_INTENDED
-#define M_FALLTHROUGH_INTENDED \
-  do {                         \
-  } while (0)
-#endif
+#define M_FALLTHROUGH_INTENDED [[fallthrough]]