Only emit definitions if !SyntaxOnly.
Only emit definitions if !SyntaxOnly.

Fixes duplicate definition errors with PCH, where the first definition is in the PCH, and the
second one is injected at runtime, after attaching the PCH.
This patch still exposes as many declarations as possible to fSyntaxOnly to validate their syntax.

zzxuanyuan/root,zzxuanyuan/root,karies/root,karies/root,root-mirror/root,mhuwiler/rootauto,karies/root,simonpf/root,olifre/root,karies/root,root-mirror/root,zzxuanyuan/root,karies/root,zzxuanyuan/root,karies/root,olifre/root,root-mirror/root,mhuwiler/rootauto,simonpf/root,mhuwiler/rootauto,karies/root,simonpf/root,root-mirror/root,simonpf/root,mhuwiler/rootauto,simonpf/root,root-mirror/root,mhuwiler/rootauto,root-mirror/root,root-mirror/root,olifre/root,karies/root,mhuwiler/rootauto,zzxuanyuan/root,root-mirror/root,simonpf/root,olifre/root,karies/root,olifre/root,simonpf/root,olifre/root,simonpf/root,olifre/root,mhuwiler/rootauto,zzxuanyuan/root,zzxuanyuan/root,zzxuanyuan/root,root-mirror/root,karies/root,zzxuanyuan/root,root-mirror/root,simonpf/root,mhuwiler/rootauto,simonpf/root,mhuwiler/rootauto,zzxuanyuan/root,mhuwiler/rootauto,root-mirror/root,zzxuanyuan/root,karies/root,zzxuanyuan/root,olifre/root,mhuwiler/rootauto,olifre/root,olifre/root,olifre/root,simonpf/root