[ISSUE] Retroarch 1.13: "Failed to compile vertex shader stage" after second launch of core

[ISSUE] Retroarch 1.13: "Failed to compile vertex shader stage" after second launch of core

[twingofan]

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New issue by twingofan on void-packages repository

https://github.com/void-linux/void-packages/issues/41015

Description:
### Is this a new report?

Yes

### System Info

Void 6.0.10_1 x86_64 GenuineIntel uptodate FFFFFFF

### Package(s) Affected

retroarch-1.13.0_1

### Does a report exist for this bug with the project's home (upstream) and/or another distro?

https://github.com/libretro/RetroArch/issues/13583
https://bugs.archlinux.org/task/73585

### Expected behaviour

Retroarch should allow the user to freely apply and edit slang and glsl shaders to its various emulator cores. Void's Retroarch package seems to handle glsl shaders correctly through the gl graphics driver, but has problems with slang shaders under the Vulkan or coregl drivers.

### Actual behaviour

When using Vulkan or coregl, Retroarch will not apply slang shaders after the second time a core is launched without restarting the entire program, leaving an `[ERROR] [slang]: Failed to compile vertex shader stage.` message in the logs. 

The issue seems to lie with the `--disable-builtin-slang` build option, and the Arch package maintainer solved the problem by removing it from their builds. As discussed in the upstream bugreport, it's possible this is part of a deeper issue with either Retroarch or glslang, but the quick and dirty fix of just removing the build option from the xbps template appears to solve the issue without causing any immediately obvious problems, i.e. "works on my machine".

### Steps to reproduce

1. Launch Retroarch with the coregl or Vulkan graphics drivers for slang shader support
2. Load and run a core with content, applying a slang shader preset from the quick options menu 
3. Shaders should apply correctly, even when loading different presets or toggling on and off
4. Close the content/core
5. Without closing Retroarch, reload a core and attempt to apply a slang shader preset
6. All shaders will fail to apply until a full restart of Retroarch