Fix zlib old-style-cast build breakage

[droe]

Summary

Build "Fix zlib old-style-cast build breakage"

Purpose of change

Unbreak the build on at least macOS Sonoma with Xcode 15.2 (15C500b) and zlib 1.3.1 from MacPorts; possibly also on other platform / compiler / zlib combinations:

clang++ -Isrc -isystem src/third-party -DMACOSX -DGIT_VERSION -DOSX_SDL2_LIBS -DTILES -DBACKTRACE -DUSE_HOME_DIR -Og -Werror -Wall -Wextra -Wformat-signedness -Wlogical-op -Wmissing-declarations -Wmissing-noreturn -Wnon-virtual-dtor -Wold-style-cast -Woverloaded-virtual -Wpedantic -Wsuggest-override -Wunused-macros -Wzero-as-null-pointer-constant -Wno-unknown-warning-option -Wno-dangling-reference -Wno-c++20-compat -Wredundant-decls  -g  -fsigned-char -stdlib=libc++ -std=c++17 -DIMGUI_DISABLE_OBSOLETE_KEYIO -mmacosx-version-min=10.13 -D_THREAD_SAFE -I/opt/local/include/SDL2 -I/opt/local/include -I/opt/local/include/opus -I/opt/local/include -I/opt/local/include/opus -I/opt/local/include -I/opt/local/include/SDL2 -DSDL_SOUND -I/opt/local/include/SDL2 -D_THREAD_SAFE -I/opt/local/include -MMD -MP -Winvalid-pch -include-pch pch/main-pch.hpp.pch -c src/cata_utility.cpp -o obj/tiles/cata_utility.o
src/cata_utility.cpp:402:9: error: use of old-style cast [-Werror,-Wold-style-cast]
    if( inflateInit2( &zs, MAX_WBITS | 16 ) != Z_OK ) {
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/local/include/zlib.h:1822:25: note: expanded from macro 'inflateInit2'
                        (int)sizeof(z_stream))
                        ^    ~~~~~~~~~~~~~~~~
1 error generated.
make: *** [obj/tiles/cata_utility.o] Error 1

Describe the solution

Disable -Wold-style-cast across the use of zlib's inflateInit2 macro.

Describe alternatives you've considered

That macro uses a C style cast because it lives in a (C++-compatible) C header, so this isn't a bug in zlib, and even if it were, we'd still want to work around (hypothetically) broken zlib versions.

Considered removing either -Werror or -Wold-style-cast from the defaults, but felt that would be a more contentious change than locally disabling -Wold-style-cast (i.e. the footgunning seems intentional).

Testing

Before change: Build was broken. After change: Build was fine. Smoke-tested the resulting binaries and they seem fine.

Additional context

n/a