How to reproduce:
1. Open the attached 'PostProcessShaderWarmupIssue-2019.4.zip' project
2. Switch Target Platform to iOS in the Build Settings
3. Select Run as Xcode as Debug
4. Build for iOS and open the Xcode project
5. Deploy the Xcode project to an iOS device
6. Press 'Warmup' button once the application is opened

Expected result: GPU doesn't crash and errors do not occur when Shader.WarmupAllShaders() method is invoked
Actual result: GPU crashes and 'Compiler failed to build request Metal: Error creating pipeline state (Hidden/Universal Render Pipeline/GaussianDepthOfField): fragment shader color output does not have enough components for the pixel format (MTLPixelFormatBGRA8Unorm_sRGB)' error is thrown in the Console when Shader.WarmupAllShaders() method is invoked

Reproducible with: 2019.3.0b3(7.0.1), 2019.4.6f1(7.3.1, 7.4.1), 2020.1.0a4(7.0.1), 2020.1.0f1(8.2.0), 2020.2.0a19(8.2.0)
Not reproducible with: 2018.4.26f1(4.1.0), 2019.3.0b2(7.0.1), 2020.1.0a3(7.0.1)

Reproducible with:
iPhone 8+ (iOS 12.0)
iPhone XR (iOS 13.4.1)
iPad Air 2 (iOS 11.0.3)
iPad 9.7 6th gen (iOS 12.1)
Mac Standalone

Not reproducible with:
Windows Standalone

Notes:
- Reproducible on Metal; Not reproducible on Open GLES 2, Open GLES 3, DX11
- Not reproducible with built-in pipeline
- In 2019.3.0b1 warm-up is executed with no errors, in 2019.3.0b2 errors are thrown but after that warm up is executed, in 2019.3.0b3 only errors occur