in musl cstdint is not included by including other headers. It has to be specifically included.

--- a/dep/scid/code/src/bytebuf.h
+++ b/dep/scid/code/src/bytebuf.h
@@ -34,6 +34,7 @@
 #include <cassert>
 #include <cstring>
 #include <string_view>
+#include <cstdint>
 
 /**
  * The Tag section is a list of <tag,value> variable length records:
