Reduce the cyclomatic complexity of our Python code

Our automated tests currently run ruff --max-complexity=101 when the recommended setting is 10, not 101. We do not need to reduce complexity all the way down to 10 but we should examine our worst offending functions and try to reduce their cyclomatic complexity.

Strong tests should be put in place before modifying these functions because at 101, we should expect severe spaghetti code with substantial corner cases and side effects. GenerateOutput() is one function that is 739 lines long!

Please modify only one file per pull request given the difficulty of reviewing changes to older yet crucial code.

% flake8 --ignore=E203,W503 --max-line-length=88 --statistics --max-complexity=20

./gyp/pylib/gyp/generator/xcode.py:641:1: C901 'GenerateOutput' is too complex (101)
./gyp/pylib/gyp/generator/cmake.py:624:1: C901 'WriteTarget' is too complex (78)
./gyp/pylib/gyp/generator/ninja.py:2207:1: C901 'GenerateOutputForConfig' is too complex (55)
./gyp/pylib/gyp/input.py:759:1: C901 'ExpandVariables' is too complex (48)
./gyp/pylib/gyp/__init__.py:316:1: C901 'gyp_main' is too complex (45)
./gyp/pylib/gyp/generator/make.py:1571:5: C901 'MakefileWriter.WriteTarget' is too complex (40)
./gyp/pylib/gyp/generator/ninja.py:1349:5: C901 'NinjaWriter.WriteLinkForArch' is too complex (35)
./gyp/pylib/gyp/generator/make.py:2230:1: C901 'GenerateOutput' is too complex (34)
./gyp/pylib/gyp/xcode_emulation.py:571:5: C901 'XcodeSettings.GetCflags' is too complex (32)
./gyp/pylib/gyp/input.py:2529:1: C901 'ProcessListFiltersInDict' is too complex (27)
./gyp/pylib/gyp/generator/ninja.py:1057:5: C901 'NinjaWriter.WriteSourcesForArch' is too complex (25)
./gyp/pylib/gyp/generator/xcode.py:138:5: C901 'XcodeProject.Finalize1' is too complex (25)
./gyp/pylib/gyp/generator/ninja.py:378:5: C901 'NinjaWriter.WriteSpec' is too complex (24)
./gyp/pylib/gyp/MSVSNew.py:230:5: C901 'MSVSSolution.Write' is too complex (21)
./gyp/pylib/gyp/input.py:2974:1: C901 'Load' is too complex (21)
./gyp/pylib/gyp/generator/ninja.py:686:5: C901 'NinjaWriter.WriteRules' is too complex (21)
16    C901 'GenerateOutput' is too complex (101)

Coincidence: Our most complex function has a McCabe complexity of 101 and this is issue #101.

Start with gyp/pylib/gyp/generator/xcode.py and the 739-line GenerateOutput function, or choose another function from the listed complexity report. Establish strong tests before changing the selected function, then run the existing test suite and complexity check. Done means reduced cyclomatic complexity with behavior preserved and changes limited to one file.