[clang] [Serialization] Read the initializer for interesting static variables before consuming it (PR #92353)

[Ulrich Weigand via cfe-commits]

uweigand wrote:

I'm not seeing any failures with this patch on s390x with the regular check-all and check-openmp tests.  Do you have a link to the failures you were seeing in the past (was that on the build bot?)?

https://github.com/llvm/llvm-project/pull/92353