[spirv] nuke spirv-opt (#3877)

lots of AGILEism in spirv-opt
theres BETTER alternatives like https://github.com/renderbag/re-spirv (im not gonna bother for now, it probably has shitty build system)
it sucks

the IR already resolves most of the shader code to just constant load/stores
Spirv-opt passes do not seem to make such a big difference
only introduce extra latency
like for example cbuf pass in IR already removes a lot of code, that spirv_opt would otherwise miss due to the fact it doesn't have cbuf information

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

Co-authored-by: crueter <crueter@eden-emu.dev>
Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/3877
Reviewed-by: CamilleLaVey <camillelavey99@gmail.com>
Reviewed-by: crueter <crueter@eden-emu.dev>

externals/ffmpeg/CMakeLists.txt

@@ -1,4 +1,4 @@
-# SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+# SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
 # SPDX-License-Identifier: GPL-3.0-or-later
 
 # SPDX-FileCopyrightText: 2021 yuzu Emulator Project
@@ -254,7 +254,7 @@ else()
         OUTPUT
             ${FFmpeg_BUILD_LIBRARIES}
         COMMAND
-            make ${FFmpeg_MAKE_ARGS}
+            gmake ${FFmpeg_MAKE_ARGS}
         WORKING_DIRECTORY
             ${FFmpeg_BUILD_DIR}
     )