chore: make yuzu REUSE compliant

[REUSE] is a specification that aims at making file copyright
information consistent, so that it can be both human and machine
readable. It basically requires that all files have a header containing
copyright and licensing information. When this isn't possible, like
when dealing with binary assets, generated files or embedded third-party
dependencies, it is permitted to insert copyright information in the
`.reuse/dep5` file.

Oh, and it also requires that all the licenses used in the project are
present in the `LICENSES` folder, that's why the diff is so huge.
This can be done automatically with `reuse download --all`.

The `reuse` tool also contains a handy subcommand that analyzes the
project and tells whether or not the project is (still) compliant,
`reuse lint`.

Following REUSE has a few advantages over the current approach:

- Copyright information is easy to access for users / downstream
- Files like `dist/license.md` do not need to exist anymore, as
  `.reuse/dep5` is used instead
- `reuse lint` makes it easy to ensure that copyright information of
  files like binary assets / images is always accurate and up to date

To add copyright information of files that didn't have it I looked up
who committed what and when, for each file. As yuzu contributors do not
have to sign a CLA or similar I couldn't assume that copyright ownership
was of the "yuzu Emulator Project", so I used the name and/or email of
the commit author instead.

[REUSE]: https://reuse.software

Follow-up to b2eb10382941bef0914f4a0a4685b9033440aa9f

3 files changed, 10 insertions, 4 deletions

diff --git a/externals/cmake-modules/GetGitRevisionDescription.cmake b/externals/cmake-modules/GetGitRevisionDescription.cmake
index 087f5deeae..dab1347753 100644
--- a/externals/cmake-modules/GetGitRevisionDescription.cmake
+++ b/externals/cmake-modules/GetGitRevisionDescription.cmake
@@ -1,3 +1,7 @@
+# SPDX-FileCopyrightText: 2009 Iowa State University
+# SPDX-FileContributor: Ryan Pavlik <rpavlik@iastate.edu> <abiryan@ryand.net>
+# SPDX-License-Identifier: BSL-1.0
+
 # - Returns a version string from Git
 #
 # These functions force a re-configure on each git commit so that you can
diff --git a/externals/cmake-modules/GetGitRevisionDescription.cmake.in b/externals/cmake-modules/GetGitRevisionDescription.cmake.in
index 0d7eb3c265..868e032efb 100644
--- a/externals/cmake-modules/GetGitRevisionDescription.cmake.in
+++ b/externals/cmake-modules/GetGitRevisionDescription.cmake.in
@@ -1,4 +1,7 @@
-# 
+# SPDX-FileCopyrightText: 2009 Iowa State University
+# SPDX-FileContributor: Ryan Pavlik <rpavlik@iastate.edu> <abiryan@ryand.net>
+# SPDX-License-Identifier: BSL-1.0
+
 # Internal file for GetGitRevisionDescription.cmake
 #
 # Requires CMake 2.6 or newer (uses the 'function' command)
diff --git a/externals/cmake-modules/WindowsCopyFiles.cmake b/externals/cmake-modules/WindowsCopyFiles.cmake
index 72cec53549..08b598365d 100644
--- a/externals/cmake-modules/WindowsCopyFiles.cmake
+++ b/externals/cmake-modules/WindowsCopyFiles.cmake
@@ -1,6 +1,5 @@
-# Copyright 2018 Yuzu Emulator Project
-# Licensed under GPLv2 or any later version
-# Refer to the license.txt file included.
+# SPDX-FileCopyrightText: 2018 yuzu Emulator Project
+# SPDX-License-Identifier: GPL-2.0-or-later
 
 # This file provides the function windows_copy_files.
 # This is only valid on Windows.