Add driver test for multiple preprocessor inputs

Fix an unintentional stdin read in the darwin-asan-nofortify.c test and replace
it with an explicit test for multiple -E inputs passed to the driver.

Noticed while working on the in-process driver patch.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@202007 91177308-0d34-0410-b5e6-96231b3b80d8