Fixed some rtti-options tests.

Certain tests in rtti-options.cpp are not really testing anything because they are testing for the absence of -frtti option to the cc1 process. Since the cc1 process does not take -frtti option, these tests are passing tautologically.

The RTTI mode is enabled by default in cc1, and -fno-rtti disables it. Therefore the correct way to check for enabling of RTTI is to check for the absence of -fno-rtti to cc1, and the correct way to check for disabling of RTTI is to check for the presence of -fno-rtti to cc1.

This patch fixes those tests.

Differential Revision: https://reviews.llvm.org/D46836

llvm-svn: 332384