Err, instead of warn, if mutex / atomic / unicode funcs are missing
Hopefully this results in fewer badly built HarfBuzz integrations.
diff --git a/src/hb-unicode.cc b/src/hb-unicode.cc
index fc19006..b598a95 100644
--- a/src/hb-unicode.cc
+++ b/src/hb-unicode.cc
@@ -147,11 +147,11 @@
#if !defined(HB_NO_UNICODE_FUNCS) && defined(HB_UNICODE_FUNCS_NIL)
#ifdef _MSC_VER
-#pragma message("Could not find any Unicode functions implementation, you have to provide your own")
-#pragma message("To suppress this warnings, define HB_NO_UNICODE_FUNCS")
+#pragma error("Could not find any Unicode functions implementation, you have to provide your own.")
+#pragma error("Consider building hb-ucdn.c. If you absolutely want to build without any, check the code.")
#else
-#warning "Could not find any Unicode functions implementation, you have to provide your own"
-#warning "To suppress this warning, define HB_NO_UNICODE_FUNCS"
+#error "Could not find any Unicode functions implementation, you have to provide your own"
+#error "Consider building hb-ucdn.c. If you absolutely want to build without any, check the code."
#endif
#endif
