* Use a single stat to find out if the file exists and if it is a regular file.
* Use early returns when possible.
* Add comments explaining why we have each check.
llvm-svn: 185091
- This is designed to make it obvious that %clang_cc1 is a "test variable"
which is substituted. It is '%clang_cc1' instead of '%clang -cc1' because it
can be useful to redefine what gets run as 'clang -cc1' (for example, to set
a default target).
llvm-svn: 91446
Aaron Ballman