Align build script with unified Zig + Nix pattern

- ./build uses nix build + install to zig-out/bin/ (canonical location)
- ./build debug uses zig build directly with Debug optimization
- flake.nix updated to ReleaseFast to match

Author: Peter Marreck

build

@@ -1,10 +1,29 @@
 #!/usr/bin/env bash
-set -euo pipefail
+set -uo pipefail
+set -E
 
-if command -v nix >/dev/null 2>&1; then
-  nix build "$@"
+trap 'echo "ERR at ${BASH_SOURCE[0]}:${LINENO}: $BASH_COMMAND" >&2' ERR
+
+run() {
+  "$@" || {
+    echo "FAILED: $*" >&2
+    exit 1
+  }
+}
+
+optimize="ReleaseFast"
+if [[ "${1:-}" == "debug" ]]; then
+  optimize="Debug"
+  shift
+fi
+
+if [[ "$optimize" != "ReleaseFast" ]]; then
+  # Non-release builds use zig directly (local dev, no need for Nix reproducibility)
+  run zig build "-Doptimize=$optimize" "$@"
+elif command -v nix >/dev/null 2>&1; then
+  run nix build "$@"
   mkdir -p zig-out/bin
-  install -m755 result/bin/* zig-out/bin/
+  run install -m755 result/bin/* zig-out/bin/
 else
-  zig build -Doptimize=ReleaseSafe "$@"
+  run zig build "-Doptimize=$optimize" "$@"
 fi

flake.nix

@@ -61,7 +61,7 @@
 
 						zig build \
 							--system ${zigPkgCache} \
-							-Doptimize=ReleaseSafe \
+							-Doptimize=ReleaseFast \
 							--color off
 					'';