__has_attribute now understands target-specific attributes. So when you ask...

__has_attribute now understands target-specific attributes. So when you ask whether an ARM target has the "interrupt" attribute, it will return true for ARM and MSP430 targets, and false for others.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@198897 91177308-0d34-0410-b5e6-96231b3b80d8