tree bb47da2df0ebaf309e71653d3b6ae07b76c39197
parent 39336b04b15040237cc298da9756a16945054d57
author Dennis Kormalev <denk@google.com> 1656019117 +0000
committer CQ Bot Account <pigweed-scoped@luci-project-accounts.iam.gserviceaccount.com> 1656019117 +0000

pw_span: Include system span header only if fresh enough

Before this CL polyfill span was always included and relied on the
__cpp_lib_span define. Some older standard libraries could have this one
not defined which leads to ambiguity during compilation.
This CL fetches __cpp_lib_span version first and includes system span
header only if version is good enough, otherwise it fall backs to custom
implementation.

Change-Id: Ia20e649a2893259929f500154e2d74366feb2ca4
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/99540
Reviewed-by: Wyatt Hepler <hepler@google.com>
Pigweed-Auto-Submit: Dennis Kormalev <denk@google.com>
Commit-Queue: Auto-Submit <auto-submit@pigweed.google.com.iam.gserviceaccount.com>