We don't need `file_actions` to be a constant-reference. It's created
in-place by its one user (HackStudio). Because it is currently a const-
ref, if we try to create a ProcessSpawnOptions like so:
Core::ProcessSpawnOptions options { .name = "foo"sv };
We get the following error with clang 18:
lifetime extension of temporary created by aggregate initialization
using a default member initializer is not yet supported; lifetime of
temporary will end at the end of the full-expression
207f3f1cb4