Fix gcc 9 warnings.

GCC 9 warns about this pessimizing-move. It isn't clear why clang isn't
as well.

GCC 9 has a working redundant-move diagnostic. Clang has an old (C++11
style) redundant-move diagnostic which only warns when moving a
parameter. The GCC warning conflicts with Clang's
return-std-move-in-c++11, which we want to keep until we can drop
support for older compilers. So just disable redundant-move warnings
until we can remove return-std-move-in-c++11.

This change allows us to compile without warnings on gcc 9.3.0.

Change-Id: If21fcfb2944ce49e27fc84d40805752895ae68cf
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/279958
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>
2 files changed