First I ran ClangBuildAnalyzer without the precompiled headers enabled to determine the heavy ones. Then I ran it again with the precompiled headers enabled to see if there were more beyond the top 10 ones.

In case of lib there is no change - mainly because it's just different headers which lead up to the same stuff being included. For test there's a very slight improvement only.

For cppcheck-gui there's obviously a big improvement since we had none so far:

before:

Compilation (86 times):
  Parsing (frontend):          392.1 s
  Codegen & opts (backend):    119.2 s

after:

Compilation (87 times):
  Parsing (frontend):           96.7 s
  Codegen & opts (backend):    136.2 s