meson: Disable GCC's dead store elimination for memory zeroing custom new

meson: Disable GCC's dead store elimination for memory zeroing custom new

Some classes use custom new operator which zeroes memory, however gcc does
aggressive dead-store elimination which threats all writes to the memory
before the constructor as "dead stores".

For now we disable this optimization.

The new operators in question are declared via:
 DECLARE_RZALLOC_CXX_OPERATORS
 DECLARE_LINEAR_ZALLOC_CXX_OPERATORS

The issue was found with lto builds, however there is no guarantee that
it didn't happen with ordinary ones.

CC: <mesa-stable@lists.freedesktop.org>
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/2977
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/1358
Signed-off-by: Danylo Piliaiev <danylo.piliaiev@globallogic.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5104>