Fix output file update on dry-run compile

[atugushev]

Fixes #841

Changelog-friendly one-liner: Fix output file update in dry-run mode in pip-compile

Contributor checklist

• Provided the tests for the changes.
• Requested a review from another contributor.
• Gave a clear one-line description in the PR (that the maintainers can add to CHANGELOG.md on release).
• Assign the PR to an existing or new milestone for the target version (following Semantic Versioning).

[codecov]

Codecov Report

Merging #842 into master will decrease coverage by 0.07%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #842      +/-   ##
==========================================
- Coverage   98.84%   98.76%   -0.08%     
==========================================
  Files          36       36              
  Lines        2172     2194      +22     
  Branches      285      285              
==========================================
+ Hits         2147     2167      +20     
- Misses         15       16       +1     
- Partials       10       11       +1

Impacted Files	Coverage Δ
piptools/utils.py	100% <100%> (ø)	⬆️
tests/test_cli_compile.py	100% <100%> (ø)	⬆️
tests/test_sync.py	98.74% <0%> (-1.26%)	⬇️

---

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[codecov]

Codecov Report

Merging #842 into master will decrease coverage by 0.07%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #842      +/-   ##
==========================================
- Coverage   98.84%   98.76%   -0.08%     
==========================================
  Files          36       36              
  Lines        2172     2194      +22     
  Branches      285      285              
==========================================
+ Hits         2147     2167      +20     
- Misses         15       16       +1     
- Partials       10       11       +1

Impacted Files	Coverage Δ
piptools/utils.py	100% <100%> (ø)	⬆️
tests/test_cli_compile.py	100% <100%> (ø)	⬆️
tests/test_sync.py	98.74% <0%> (-1.26%)	⬇️

---

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 becc4dc...3e632c5. Read the comment docs.

[atugushev]

pip-tools v3.9.0 is released.