For loops over find output are fragile. Use find -exec or a while read loop.

Resolves #81

Please check if the PR fulfills these requirements

[x] The commit message follows our guidelines: https://github.com/HackedByChinese/ng2-idle/blob/master/CONTRIBUTING.md#pr
[ ] Tests for the changes have been added (for bug fixes / features)
[ ] Docs have been added / updated (for bug fixes / features)

What kind of change does this PR introduce? (check one with "x")

[ ] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[x] Build related changes
[ ] CI related changes
[ ] Other... Please describe:

What is the current behavior? (You can also link to an open issue here)

81

What is the new behavior?

for d in (find ...) do ... has been replaced by find -exec ...
process.env.MODE has been replaced process.env.npm_config_mode
- this change allows passing the MODE as an argument: npm run build:umd --mode=ugly

Does this PR introduce a breaking change? (check one with "x")

[ ] Yes
[x] No

If this PR contains a breaking change, please describe the impact and migration path for existing applications: ...

Other information: https://github.com/koalaman/shellcheck/wiki/SC2044

moribvndvs / ng2-idle

chore: use find -exec #82

81