[Engine Examples] - local build time gets progressively slower

[mvaligursky]

I locally build examples using npm run develop, and then modify the source code of both the examples and the engine. I've noticed that the build time gets longer each build, forcing me to restart the command every 20 or so builds.

See how this progressed from 0.8s to 2.2s over about 15 builds:

Note that I also run target=debug_es5 npm run watch in the engine to have up to date engine build, which might but might not be related.

pinging @kungfooman in case he has some ideas here.

[kungfooman]

Interesting, I can reproduce.

Saving random changes in engine only while running npm run develop always takes around ~300-500ms:

When I add run target=debug_es5 npm run watch in another shell the file watcher goes crazy:

Examples build script starts to even rebuild multiple times.

Pretty sure this can be fixed when we stop putting watchers on build outputs and instead use the rollup target configuration functions (e.g. function buildTarget(buildType, moduleFormat)) directly in examples/rollup.config.js for building these:

    { src: '../build/playcanvas.d.ts', dest: 'dist/playcanvas.d.ts' },
    { src: '../build/playcanvas.js', dest: 'dist/iframe/playcanvas.js' },
    { src: '../build/playcanvas.dbg.js', dest: 'dist/iframe/playcanvas.dbg.js' },
    { src: '../build/playcanvas.prf.js', dest: 'dist/iframe/playcanvas.prf.js' },
    { src: '../build/playcanvas-extras.js', dest: 'dist/iframe/playcanvas-extras.js' },

Another advantage is: we won't need npm run build in engine folder any longer (simplifying the build procedure a bit)