compiler error:size_t’ was not declared in this scope; did you mean ‘std::size_t’?

git clone source and check out v.7.0.6
and ./scripts/build.sh
error break:
size_t’ was not declared in this scope; did you mean ‘std::size_t’?
gcc (GCC) 11.1.0
clang version 13.0.0
os: manjaro

Reproduce the failure by checking out v7.0.6 and running ./scripts/build.sh on the reported Manjaro environment with GCC 11.1.0 or Clang 13. No source file or test is named, so use the build output to locate the size_t diagnostic. Done means the v7.0.6 build completes successfully without this error.

Written by the indexing model from the issue text.