With the changes in 48d0eb518, the CodeGenOptions used to emit .pcm
files with -fmodule-format=obj (-gmodules) were the ones from the
original invocation, rather than the ones specifically crafted for
outputting the pcm. This was causing the pcm to be written with only the
debug info and without the __clangast section in some cases (e.g. -O2).
This unforunately was not covered by existing tests, because compiling
and loading a module within a single compilation load the ast content
from the in-memory module cache rather than reading it from the pcm file
that was written. This broke bootstrapping a build of clang with modules
enabled on Darwin.
rdar://143418834
Fixes one of the crashes uncovered by
https://github.com/llvm/llvm-project/pull/118710
`getOrCreateStandaloneType` asserts that a `DIType` was created for the
requested type. If the `Decl` was marked `nodebug`, however, we can't
generate debug-info for it, so we would previously trigger the assert.
For now keep the assertion around and check the `nodebug` at the
callsite.
