Minify GLSL shaders in release export templates to reduce binary size

[Calinou]

This reduces release export template binary sizes by about 103 KB. To avoid interfering with debugging, only target=template_release builds make use of GLSL minification.

TODO

• Figure out how to avoid copy-pasting the list of minification replacements in both GLES3 and Vulkan builders.

[reduz]

This is really not a good idea, the shader is printed on error so it should not be modified. Instead, I would look into compressing the shader using zlib or something else like we compress docs and other things.

[Calinou]

This is really not a good idea, the shader is printed on error so it should not be modified. Instead, I would look into compressing the shader using zlib or something else like we compress docs and other things.

Note that comments are already stripped from shaders (even in target=debug builds), so line numbers printed by Godot already don't match those you find in the original shader file.

Compressing text resources in the binary is still a valuable thing, but ideally, we should do both minification and compression.

[Calinou]

I've amended the PR to avoid code duplication for the minification routine, and also changed it to only affect release export templates. The binary size reduction has also increased somewhat since I opened this PR (-90 KB -> -103 KB on a stripped Linux x86_64 release export template with LTO).

[Calinou]

Rebased and tested again, it works as expected.

The binary size improvement has further increased since I last tested this PR (sizes are for a Linux x86_64 release export template, stripped with LTO):

• master: 71,782,136 bytes
• This PR: 71,503,608 bytes

That's a difference of almost 280 KB. This is likely due to the inclusion of a lot more GLSL code nowadays (e.g. for FSR2).