Two changes:

1. Don't bother truncating reading of the file. It doesn't save that much
   time and we should support putting RUN lines anywhere in the file. For
   example, someone might want to put the grep match before each function
   in the test file which would sprinkle the RUN: lines throughout the file.
2. Fix a bug with llvmgcc version match .. global var wasn't declared as such

llvm-svn: 36085