Fix PRE_BUILD step for VS generator and PCH REUSE_FROM.

7 jobs for !4724 with fix-multiple-pch-object-inputs in 4 minutes and 7 seconds (queued for 2 seconds)
latest detached
Status Job ID Name Coverage
  Build
passed #4941029
linux docker build
build:debian10-iwyu

00:04:07

passed #4941031
linux-3.17 linux docker build
build:fedora31-sphinx

00:03:23

passed #4941030
linux docker build
build:fedora31-tidy

00:01:47

 
  External
passed cdash

passed ghostflow-check-master

passed cdash

passed cdash