Switch build commands to use process utils

[jonahwilliams]

Description

This is just a higher level wrapper around the same code we are calling. No tests are effected because we are still correctly mocking/asserting the lower level and behavior is unchanged.

Fixes #42261

[fluttergithubbot]

It looks like this pull request may not have tests. Please make sure to add tests before merging. If you need an exemption to this rule, contact Hixie.

Reviewers: Read the Tree Hygiene page and make sure this patch meets those guidelines before LGTMing.

[christopherfujino]

lgtm!

[codecov]

Codecov Report

Merging #42373 into master will decrease coverage by 0.46%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master   #42373      +/-   ##
==========================================
- Coverage   60.28%   59.81%   -0.47%     
==========================================
  Files         194      194              
  Lines       18868    18962      +94     
==========================================
- Hits        11374    11343      -31     
- Misses       7494     7619     +125

Flag	Coverage Δ
#flutter_tool	59.81% <100%> (-0.47%)	⬇️

Impacted Files	Coverage Δ
...s/flutter_tools/lib/src/windows/build_windows.dart	81.25% <100%> (-4.12%)	⬇️
...kages/flutter_tools/lib/src/macos/build_macos.dart	90% <100%> (-2.31%)	⬇️
...kages/flutter_tools/lib/src/linux/build_linux.dart	83.87% <100%> (-3.63%)	⬇️
...utter_tools/lib/src/macos/cocoapods_validator.dart	47.82% <0%> (-34.79%)	⬇️
...ckages/flutter_tools/lib/src/platform_plugins.dart	49.5% <0%> (-28.72%)	⬇️
...ages/flutter_tools/lib/src/linux/linux_device.dart	44.44% <0%> (-26.99%)	⬇️
packages/flutter_tools/lib/src/dart/sdk.dart	80% <0%> (-20%)	⬇️
packages/flutter_tools/lib/src/features.dart	83.33% <0%> (-14.23%)	⬇️
packages/flutter_tools/lib/src/base/io.dart	53.33% <0%> (-11.54%)	⬇️
packages/flutter_tools/lib/src/ios/devices.dart	65.97% <0%> (-9.33%)	⬇️
... and 38 more

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