"ES shaders for SPIR-V require version 310 or higher" when only pre-processing with -E

[speedym]

Even though I'm using -E switch for pre-processing only, glslc shows the following error: "ES shaders for SPIR-V require version 310 or higher" for shaders which have #version 300 es as their first line.

I would expect glslc to skip this error check when -E switch is specified.

Workaround for this issue is to specify -std=320es parameter, which disables (hacks around) that error, and (hopefully) does not affect the pre-processing results.

[zoddicus]

@dneto0 can you take a look at this?