Do not watch unless --watch is specified explicitly

[lukastaegert]

This PR contains:

• bugfix
• feature
• refactor
• documentation
• other

Are tests included?

• yes (bugfixes and features will not be merged without tests)
• no

Breaking Changes?

• yes (breaking changes will not be merged unless absolutely necessary)
• no

List any relevant issue numbers:
Resolves #3967

Description

If someone specifies e.g. rollup --no-watch.clearScreen but not --watch, we should not watch.

[github-actions]

Thank you for your contribution! ❤️

You can try out this pull request locally by installing Rollup via

npm install rollup/rollup#gh-3967-fix-cli-watch

or load it into the REPL:
https://rollupjs.org/repl/?pr=4335

[codecov]

Codecov Report

Merging #4335 (6a0bfb6) into master (7f55571) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #4335   +/-   ##
=======================================
  Coverage   98.44%   98.44%           
=======================================
  Files         205      205           
  Lines        7314     7320    +6     
  Branches     2084     2085    +1     
=======================================
+ Hits         7200     7206    +6     
  Misses         55       55           
  Partials       59       59           

Impacted Files	Coverage Δ
cli/run/index.ts	100.00% <100.00%> (ø)
src/utils/options/mergeOptions.ts	100.00% <100.00%> (ø)
src/utils/options/options.ts	100.00% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 7f55571...6a0bfb6. Read the comment docs.