Silence warning about detecting number of threads
Silence warning about detecting number of threads

gtest can't currently detect the number of threads in a process on
Linux, so it outputs a warning during death tests. This silences that
warning.

ongardie/gtest,y-higuchi/gtest,logcabin/gtest,y-higuchi/gtest,PlatformLab/gtest,ongardie/gtest,SMatsushi/gtest,ongardie/gtest,PlatformLab/gtest,ongardie/gtest,logcabin/gtest,SMatsushi/gtest,logcabin/gtest,y-higuchi/gtest,SMatsushi/gtest,PlatformLab/gtest,y-higuchi/gtest