Steps to reproduce:
1) Open Unity and select new LWRP template
2) Update LWRP and postProcessing packages to the latest
3) Switch to Android platform in the Build Settings
4) Make sure Vulkan is the only API in the Player Settings
5) Build this project
Observe: At the end of the building process there will be some Shader errors
Note: It will not stop the building process

Reproduced with:
2019.1.0a7, 2019.1.0a8

LWRP package: 5.0.0
PostProcessing package: 2.0.17

Error example:
Shader error in 'Hidden/PostProcessing/Uber': '#extension' : extension not supported: GL_AMD_vertex_shader_layer at line 4 (on vulkan)
Shader error in 'Hidden/PostProcessing/Uber': '#extension' : extra tokens -- expected newline at line 4 (on vulkan)
Shader error in 'Hidden/PostProcessing/Uber': '' : compilation terminated at line 4 (on vulkan)
Shader error in 'Hidden/PostProcessing/FinalPass': '#extension' : extension not supported: GL_AMD_vertex_shader_layer at line 4 (on vulkan)