Handle case when dist folder does not exist in build script

[dferber90]

The build script currently fails with Error: ENOENT: no such file or directory, stat './dist' the first time anyone clones this repo and runs npm run build.

This happens because the dist folder does not exist yet, so rmdirSync(DIR, { recursive: true }); can't remove it.

To reproduce:

rm -rf dist
npm run build

This is fixed by ignoring the ENOENT error.

[mrmckeb]

Good catch, and great work as always @dferber90!