Make Gentoo GNU GCC Config override whitespace tolerant

The config-*triple* file handling isn't tolerant of 
leading/trailing whitespace, making it not terribly 
obvious when a single extraneous tab/space/etc will 
cause the override to be ignored. This patch simply 
trims the lines to ensure that it is tolerant of 
whitespace.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@300328 91177308-0d34-0410-b5e6-96231b3b80d8