`ngtsc` currently fails building a flat module out file on Windows because it generates an invalid flat module TypeScript source file. e.g:
```ts
5 export * from './C:\Users\Paul\Desktop\test\src\export';
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
```
This is because `path.posix.relative` does not properly with non-posix paths, and only expects posix paths in order to work.
PR Close#27993
This commit adds tracking of modules, directives, and pipes which are made
visible to consumers through NgModules exported from the package entrypoint.
ngtsc will now produce a diagnostic if such classes are not themselves
exported via the entrypoint (as this is a requirement for downstream
consumers to use them with Ivy).
To accomplish this, a graph of references is created and populated via the
ReferencesRegistry. Symbols exported via the package entrypoint are compared
against the graph to determine if any publicly visible symbols are not
properly exported. Diagnostics are produced for each one which also show the
path by which they become visible.
This commit also introduces a diagnostic (instead of a hard compiler crash)
if an entrypoint file cannot be correctly determined.
PR Close#27743
This commit moves the FlatIndexGenerator to its own package, in preparation
to expand its capabilities and support re-exporting of private declarations
from NgModules.
PR Close#27743
