Imported from GitHub PR https://github.com/abseil/abseil-cpp/pull/1520
Fixes #1519 and removes the burden of manually feature testing all the platforms supported by absl.
Merge 26bc4ee13a93edaeee2a21b5eff3569b806acc91 into 94b37802
Merging this change closes #1520
COPYBARA_INTEGRATE_REVIEW=https://github.com/abseil/abseil-cpp/pull/1520 from georgthegreat:feature-test-macros 26bc4ee13a93edaeee2a21b5eff3569b806acc91
PiperOrigin-RevId: 558777775
Change-Id: Ie3e1f309761c67fa233a03e42762776cd93c69b4
