Fix macOS SDL2 include paths for resid_mixer

[Riadabd]

Toolchain

> zig version
0.15.2

Issue

On a clean checkout on macOS, zig build fails because the resid_mixer dependency can’t find SDL2 headers during @cImport. Raw error log:

  install
  └─ install 1st-shot
  └─ compile exe 1st-shot ReleaseFast native 2 errors
  ~/.cache/zig/p/resid-0.5.0-CVhkLsp0CwDSJejbTOub4ir4sj1q4-yMLAr_7TcALvZV/src/resid-mixer.zig:3:13: error: C import failed
  const SDL = @cImport({
  ^~~~~~~~
  referenced by:
  update: ~/.cache/zig/p/resid-0.5.0-CVhkLsp0CwDSJejbTOub4ir4sj1q4-yMLAr_7TcALvZV/src/resid-mixer.zig:124:21
  playerThreadFunc: src/SoundManager.zig:34:27
  11 reference(s) hidden; use '-freference-trace=13' to see all references
  .zig-cache/o/b579a38a593cb21a8da784ef79e7487e/cimport.h:1:10: error: 'SDL2/SDL.h' file not found
  #include <SDL2/SDL.h>
  ^
  error: the following command failed with 2 compilation errors:
  /opt/homebrew/Cellar/zig/0.15.2/bin/zig build-exe -I/opt/homebrew/include -I/opt/homebrew/include/SDL2 -D_THREAD_SAFE -L/opt/homebrew/lib -lSDL2 -OReleaseFast -I ~/Code/zig/1st-shot/src/core/
  lodepng/ --dep movy --dep resid -Mroot=~/Code/zig/1st-shot/src/main.zig ~/.cache/zig/p/movy-0.0.4-UtRV6xTmCwBXPu130iqjXTGTuzlPjBOcT7S2SmF_pdvw/src/core/lodepng/lodepng.c -OReleaseFast -I ~/.cache/zig/p/movy-0.0.4-UtRV6xTmCwBXPu130iqjXTGTuzlPjBOcT7S2SmF_pdvw/src/core/lodepng/ -Mmovy=~/.cache/zig/p/movy-0.0.4-UtRV6xTmCwBXPu130iqjXTGTuzlPjBOcT7S2SmF_pdvw/src/movy.zig .zig-
  cache/o/0b634b7227692218aaf4542f806f7311/libsid.a -I ~/.cache/zig/p/resid-0.5.0-CVhkLsp0CwDSJejbTOub4ir4sj1q4-yMLAr_7TcALvZV/resid-cpp -I .zig-cache/i/83345b95a32f5a3bfba2443f68782617/include/resid-
  cpp -I .zig-cache/o/a6fb089e932f705ef1065695b36c6e90 --dep sidfile --dep wavwriter --dep wavloader --dep resid_cpp --dep resid_sdl --dep resid_mixer --dep sidplayer --dep zig64 -Mresid=~/.cache/zig/
  p/resid-0.5.0-CVhkLsp0CwDSJejbTOub4ir4sj1q4-yMLAr_7TcALvZV/src/resid.zig -Msidfile=~/.cache/zig/p/resid-0.5.0-CVhkLsp0CwDSJejbTOub4ir4sj1q4-yMLAr_7TcALvZV/src/sidfile.zig -Mwavwriter=~/.cache/zig/p/resid-0.5.0-CVhkLsp0CwDSJejbTOub4ir4sj1q4-yMLAr_7TcALvZV/src/wavwriter.zig -Mwavloader=~/.cache/zig/p/resid-0.5.0-CVhkLsp0CwDSJejbTOub4ir4sj1q4-yMLAr_7TcALvZV/src/
  wavloader.zig .zig-cache/o/0b634b7227692218aaf4542f806f7311/libsid.a -I .zig-cache/o/a6fb089e932f705ef1065695b36c6e90 -I ~/.cache/zig/p/resid-0.5.0-CVhkLsp0CwDSJejbTOub4ir4sj1q4-yMLAr_7TcALvZV/
  resid-cpp -I .zig-cache/i/83345b95a32f5a3bfba2443f68782617/include/resid-cpp -Mresid_cpp=~/.cache/zig/p/resid-0.5.0-CVhkLsp0CwDSJejbTOub4ir4sj1q4-yMLAr_7TcALvZV/src/resid-cpp.zig -I resid-cpp/ -I /
  usr/include/ --dep resid_cpp -Mresid_sdl=~/.cache/zig/p/resid-0.5.0-CVhkLsp0CwDSJejbTOub4ir4sj1q4-yMLAr_7TcALvZV/src/resid-sdl.zig -I /usr/include/ --dep resid_cpp -Mresid_mixer=~/.cache/
  zig/p/resid-0.5.0-CVhkLsp0CwDSJejbTOub4ir4sj1q4-yMLAr_7TcALvZV/src/resid-mixer.zig --dep sidfile --dep zig64 -Msidplayer=~/.cache/zig/p/resid-0.5.0-CVhkLsp0CwDSJejbTOub4ir4sj1q4-yMLAr_7TcALvZV/src/
  sidplayer.zig -Mzig64=~/.cache/zig/p/zig64-0.5.0-OrrYOvgZBACGKIsII5d6w596RqNmpCCJkAeQxfCsKsQW/src/zig64.zig -lc++ -lc --cache-dir .zig-cache --global-cache-dir ~/.cache/zig --name 1st-shot
  --zig-lib-dir /opt/homebrew/Cellar/zig/0.15.2/lib/zig/ --listen=-

  Build Summary: 4/7 steps succeeded; 1 failed
  install transitive failure
  └─ install 1st-shot transitive failure
  └─ compile exe 1st-shot ReleaseFast native 2 errors

  error: the following build command failed with exit code 1:
  .zig-cache/o/41438c16014b11875c927058dc3ea791/build /opt/homebrew/Cellar/zig/0.15.2/bin/zig /opt/homebrew/Cellar/zig/0.15.2/lib/zig ~/Code/zig/1st-shot .zig-cache ~/.cache/zig --seed
  0x8b232f1a -Z573023f54c52820c

Fix

• Add macOS-only SDL2 prefix handling in build.zig.
• Add SDL2 include/library paths to resid_mixer (for @cImport) and to the main executable (for linking).
• Support override via -Dsdl2-prefix=..., defaulting to the SDL2 Homebrew path (/opt/homebrew/opt/sdl2).