[PATCH 30/79] [Backport to 15] Preserve invalid SPIRV source lang literal in module...

[PATCH 30/79] [Backport to 15] Preserve invalid SPIRV source lang literal in module metadata (#1951) (#1980)

Some SPIR-V producers generate invalid source language value (invalid =
other than the enum values defined in spv::SourceLanguage). While in
many cases this is rightly translated to DW_LANG_OpenCL, the original
source language value should be preserved in LLVM module metadata for
later use by LLVM IR consumers.

Co-authored-by: Michal Paszkowski <michal@paszkowski.org>
Gbp-Pq: Name 0030-Backport-to-15-Preserve-invalid-SPIRV-source-lang-li.patch