build: add reproducible macOS, Windows and wasm cross-check scripts

The non-Linux code paths can only be compile-checked on this machine;
agents had used ad-hoc wrapper setups. These scripts make the checks
reproducible and are wired into `just check-macos`, `check-windows`,
`check-wasm` and `check-all`:
- macos-crosscheck.sh: zig cc wrappers (dropping -arch/-mmacosx-
  version-min) plus a declaration-only os/log.h stub so the few C build
  scripts compile; clippy -D warnings on all 17 cross-platform crates
  for aarch64/x86_64-apple-darwin.
- windows-crosscheck.sh: mingw toolchain and a stub fontconfig.pc;
  clippy -D warnings for x86_64-pc-windows-gnu.
- wasm-check.sh: wasm32 clippy/build and the node-based wasm tests.

Also fixes a needless_pass_by_value lint in osbytes' non-Unix branch
that only the Windows check surfaces.

Test Plan:
- just check-macos; just check-macos x86_64-apple-darwin
- just check-windows; just check-wasm

scripts/macos-crosscheck.sh

@@ -0,0 +1,61 @@
+#!/usr/bin/env bash
+# Compile-check the macOS code paths from Linux (no macOS SDK needed).
+# Uses `zig cc` wrappers for the few C build scripts in the dependency
+# tree; real macOS builds need none of this. See docs/rewrite/notes/macos-M1.md.
+# Usage: scripts/macos-crosscheck.sh [check|clippy] [target]
+set -euo pipefail
+cd "$(dirname "$0")/.."
+MODE=${1:-clippy}
+TARGET=${2:-aarch64-apple-darwin}
+case "$TARGET" in
+  aarch64-apple-darwin) ZT=aarch64-macos ;;
+  x86_64-apple-darwin) ZT=x86_64-macos ;;
+  *) echo "unsupported target $TARGET" >&2; exit 2 ;;
+esac
+W="$PWD/target/macos-cross/$ZT"
+mkdir -p "$W/stub/os" "$W/zig-cache"
+for tool in cc c++; do
+  cat > "$W/z$tool" <<EOS
+#!/usr/bin/env bash
+args=()
+skip=0
+for a in "\$@"; do
+  if [ \$skip = 1 ]; then skip=0; continue; fi
+  case "\$a" in
+    -arch) skip=1 ;;
+    -mmacosx-version-min=*|--target=*|-target) ;;
+    *) args+=("\$a") ;;
+  esac
+done
+exec zig $tool -target $ZT "\${args[@]}"
+EOS
+  chmod +x "$W/z$tool"
+done
+cat > "$W/stub/os/log.h" <<'EOS'
+#pragma once
+/* Declaration-only stand-in for the SDK header, enough for cc-rs to
+   compile the oslog crate's wrapper during a cross *check*. */
+typedef void *os_log_t;
+typedef unsigned char os_log_type_t;
+#define OS_LOG_DEFAULT ((os_log_t)0)
+os_log_t os_log_create(const char *subsystem, const char *category);
+void os_log_with_type(os_log_t log, os_log_type_t type, const char *fmt, ...);
+#define os_log(l, ...) os_log_with_type(l, 0, __VA_ARGS__)
+#define os_log_info(l, ...) os_log_with_type(l, 1, __VA_ARGS__)
+#define os_log_debug(l, ...) os_log_with_type(l, 2, __VA_ARGS__)
+#define os_log_error(l, ...) os_log_with_type(l, 16, __VA_ARGS__)
+#define os_log_fault(l, ...) os_log_with_type(l, 17, __VA_ARGS__)
+EOS
+T=${TARGET//-/_}
+export CARGO_BUILD_RUSTC_WRAPPER= RUSTC_WRAPPER=
+export "CC_$T=$W/zcc" "CXX_$T=$W/zc++" "AR_$T=zig ar" "CFLAGS_$T=-I$W/stub"
+export GETTEXT_DIR=/nonexistent ZIG_GLOBAL_CACHE_DIR="$W/zig-cache" ZIG_LOCAL_CACHE_DIR="$W/zig-cache"
+CRATES=(-p ghostty-vt -p ghostty-unicode -p ghostty-datastruct -p ghostty-os -p ghostty-input
+  -p ghostty-config -p ghostty-terminal -p ghostty-font -p ghostty-renderer -p ghostty-termio
+  -p ghostty-core -p ghostty-apprt -p ghostty-inspector -p ghostty-lib -p ghostty-crash
+  -p ghostty-bench -p ghostty-vt-capi)
+if [ "$MODE" = clippy ]; then
+  cargo clippy --target "$TARGET" "${CRATES[@]}" --lib --tests -- -D warnings
+else
+  cargo check --target "$TARGET" "${CRATES[@]}" --lib --tests
+fi