Add libglfw3-dev to linux build deps script

[cbracken]

This ensures that the OpenGL headers and GLFW are installed.

[stuartmorgan-g]

What's the context for this change? We build GLFW from source in third_party, so there shouldn't be any dependency on system GLFW headers.

[cloudwebrtc]

The #9822 needs to use glad, but libglfw3-dev does not seem to have built-in glad.h, glad source exists in third_party\glfw.

[stuartmorgan-g]

libglfw3-dev does not seem to have built-in glad.h

Glad isn't conceptually part of GLFW, so there's no reason it should. The deps folder in GLFW where it lives contains external code, like Flutter's third_party.

I'm not sure how that relates to this PR though.

[cloudwebrtc]

If this PR is to replace the third_party/glfw dependency with libglfw3-dev, we need to import another glad.h/.c to support the texture, maybe third_party/glad or add to shell/platform/glfw?
Before that I submitted a PR to flutter/buildroot#275

[cbracken]

Nope - the issue was that my laptop blew up and I picked up a loaner. It couldn't find some GL (not GLFW) headers until I installed glfw and I expect they showed up in libmesa1-dev or some similar transitive dep. Thinking about it though, I'd have thought we should be pulling that from the buildtools sysroot and not the system, so I wonder if we're not as hermetic as we should be somewhere. Will re-remove the installed packages and see if I can track it down.