[*] basic in-house cpp linting (#4039)

- add `#pragma once` to remainder files
- "correcter" defines (ANDROID), see https://groups.google.com/g/android-ndk/c/cf9_f1SLXls
- extra miscelly fixups

Signed-off-by: lizzie <lizzie@eden-emu.dev>

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/4039
Reviewed-by: MaranBr <maranbr@eden-emu.dev>
Reviewed-by: crueter <crueter@eden-emu.dev>

tools/cpp-lint.sh

@@ -0,0 +1,55 @@
+#!/bin/sh -ex
+
+# SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+# tools/../
+ROOTDIR=$(CDPATH='' cd -- "$(dirname -- "$0")/../" && pwd)
+BUILD_DIR="$ROOTDIR"/build
+SRC_DIR="$ROOTDIR"/src
+
+die() {
+    echo "-- $*" >&2
+    exit 1
+}
+
+usage() {
+    cat <<EOF
+Usage: $0 [command]
+
+Dumb script that serves as a ad-hoc cpp-linter
+
+Commands:
+    once    Check for #pragma once prescence in header files
+	osdef	Finds OS defines that are not recommended to use.
+	inchk   Check includes being valid/toolchain not being stupid
+EOF
+}
+
+while :; do
+	case "$1" in
+	once)
+        find "$SRC_DIR" -type f -name "*.h" -exec grep -L "#pragma once" {} +
+		break
+		;;
+	osdef)
+		# not recommended macros
+		PATTERN="ANDROID\|_WIN64\|__linux\|__unix\|APPLE\|__APPLE"
+		strings=("ANDROID" "_WIN64" "__linux" "__unix" "APPLE" "__APPLE" "linux" "unix")
+		for item in "${strings[@]}"; do
+			PATTERN="$PATTERN\|ifdef $item\|($item)"
+		done
+		# if statements for macros that shouldn't be if
+		strings=("_WIN32" "_AIX" "__managarm__" "__unix__" "__linux__" "__FreeBSD__" "__NetBSD__" \
+			"__OpenBSD__" "__DragonFly__" "__redox__" "__HAIKU__" "__OHOS__" "__FIREOS__")
+		for item in "${strings[@]}"; do
+			PATTERN="$PATTERN\|if $item"
+		done
+        find "$SRC_DIR" -type f -name "*.h" -exec grep -nw "$PATTERN" {} + || echo
+		break
+		;;
+	*) usage ;;
+	esac
+
+	shift
+done