"Unknown Type Name" build failure(s) — clang 12.0.1

Some type detections are failing or wrong assumptions were made. For example, with strace, old configure are doing some tests on the bool (stdbool.h) declaration but fails on:
conftest.c:84:16: error: initializer element is not a compile-time constant
         int xlcbug = 1 / (&(digs + 5)[-2 + (bool) 1] == &digs[4] ? 1 : -1);
                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# Provided by the macro AC_HEADER_STDBOOL but removed in recent release of autoconf
PackageVersionSupposed error messageFull log Bug report
g-wrap 1.9.15-3.1inttypes.h:290:8: error: unknown type name 'intmax_t'; did you mean '__intmax_t'? Log
libixion 0.16.1-3model_context.cpp:20:39: error: unknown type name 'nullptr_t'; did you mean 'std::nullptr_t'? Log
murasaki 1.68.6-13./cryptohasher.h:32:5: error: unknown type name 'byte'; did you mean 'CryptoPP::byte'? Log
rcs-blame 1.3.1-4.2inttypes.h:290:8: error: unknown type name 'intmax_t'; did you mean '__intmax_t'? Log

4 errors