Only ignore -Wdeprecated-copy if the used compiler supports the warning

This is needed after
  https://reviews.llvm.org/rG9658d045926545e62cc3f963fe611d7c5d0c9d98
which introduced code that at least didn't compile clean with clang 8.

Reviewed By: xbolva00

Differential Revision: https://reviews.llvm.org/D101288