Fix emscripten 3.1.51 breaking change about *glGetProcAddress()

[adamscott]

Since emscripten 3.1.51, a link flag is now required in order to use *glGetProcAddress() family of functions.

This PR fixes that breaking change.

We use *glGetProcAddress() (relating to the web platform) in:

• drivers/gles3/rasterizer_gles3.cpp
• drivers/gles3/storage/config.cpp

A check is done to apply the link flag -s GL_ENABLE_GET_PROC_ADDRESS only if it detects emscripten ≥ 3.1.51.

[akien-mga]

Thanks!

[dsnopek]

Hm, I don't think we should be relying on glGetProcAddress() in our web builds? If we're not compiling without this, it probably means we're missing an #ifdef WEB_ENABLED somewhere

[akien-mga]

Cherry-picked for 4.2.2.
Cherry-picked for 4.1.4.

[akien-mga]

Cherry-picked for 3.6.
Cherry-picked for 3.5.4.

[dsnopek]

I came across this one again, because I'm debugging an unrelated issue concerning Emscripten 3.1.51.

I really think this PR was the wrong way to go. As I said previously, we really shouldn't need glGetProcAddress() for the web, and if we are using it, I would consider that a bug since it's very inefficient:

If we chose not to use the -s GL_ENABLE_GET_PROC_ADDRESS flag, then any time code tried to use it on the web, it would be a compiler error, which is a nice way to prevent the "bug" of using glGetProcAddress() on the web.

[dsnopek]

Another note from the Emscripten docs about how -s GL_ENABLE_GET_PROC_ADDRESS=1 should be avoided:

[dsnopek]

Rather than just complaining, I've started draft PR #93489 :-)