for preprocessing
r300667 added support for editor placeholder to Clang. That commit didn’t take
into account that users who use Clang for preprocessing only (-E) will get the
"editor placeholder in source file" error when preprocessing their source
(PR33394). This commit ensures that Clang doesn't lex editor placeholders when
running a preprocessor only action.
rdar://32718000
Differential Revision: https://reviews.llvm.org/D34256
llvm-svn: 305576