Log Message:
openexr: update to 3.1.5.

## Version 3.1.5 (April 11, 2022)

Patch release that address various bug/build/doc issues:

* Add backwards-compatibilty flags to the core library to match
  original behavior of the the c++ library. Fixes reading of certain
  files by the new core.
* Fix build failures on MSVC14 and MSVC 2022
* Fix build failure on latest 64-bit Ubuntu
* Documentation refers to primary branch as "main"
* Update the CI workflow matrix to VFX-CY2022
* Update auto-fetch Imath version to v3.1.5