Add libclang_rt.profile-powerpc64le.a to (Optional)?ObsoleteFiles.inc

On little-endian PowerPC64, this prevented /usr/lib/clang/11.0.0 being
cleaned up completely after upgrading to clang 11.0.1.

Noticed by: pkubaj
MFC after: 4 weeks
X-MFC-With: r364284

(cherry picked from commit 7593c13e180f64a19ff4fc611f5e8955e7836466)