Pipeline overidable constants are not compile-time constant.
If a module-scope const has an [[override]] decoration, do not assign
the constant value to it, as this will propagate, and the constant value
may become inlined in places that should be overridable.
Also: Rename sem::GlobalVariable::IsPipelineConstant() to
IsOverridable() to make it clearer that this is not a compile-time known
value. Add SetIsOverridable() so we can correctly set the
IsOverridable() flag even when there isn't an ID.
Change-Id: I5ede9dd180d5ff1696b3868ea4313fc28f93af4b
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/69140
Auto-Submit: Ben Clayton <bclayton@google.com>
Reviewed-by: James Price <jrprice@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
6cdb1bf7c0