Description
When using the built-in variable sample_mask in a wgsl fragment shader, naga produces incorrect glsl, leading to a panic when using OpenGL.

Repro steps
Given the following wgsl (which I will call sample_mask.wgsl):

@fragment
fn main(@builtin(sample_mask) sample_mask: u32) -> @location(0) vec4<f32> {
    return vec4<f32>(0.0);
}

Running the command naga sample_mask.wgsl sample_mask.frag produces the following output:

#version 310 es

precision highp float;
precision highp int;

layout(location = 0) out vec4 _fs2p_location0;

void main() {
    uint sample_mask = gl_SampleMaskIn;
    _fs2p_location0 = vec4(0.0);
    return;
}

The problematic line is line 9:

uint sample_mask = gl_SampleMaskIn;

According to the spec, gl_SampleMaskIn is an array, so the correct line should be:

uint sample_mask = gl_SampleMaskIn[0];

Additionally, according to the spec, it appears that gl_SampleMaskIn is only supported in GLES version 3.20, so naga should probably also update the first line from #version 310 es to #version 320 es.

Expected vs observed behavior
Shaders using sample_mask works fine in Vulkan and DX12, but cause a panic in OpenGL.

Platform
This happens both when using the naga command line version 22.0.0, in a simple test program using wgpu 22.1.0, and in my application that uses wgpu 0.20.0.