Pick correct compilerOptions when checking if we can share emitSignatures

[sheetalkamat]

OldCompilerOptions is set only if referencemaps are created vs not created. Module.None does not create reference map but other values do create it. Which is what determines if we can say copy semantic diagnostics etc.. But emit signatures are purely based on declaration path and their contents so they should only use the compilerOptions directly from old state.

Fixes #50902