Tidy up JavacFlagBuilder

[ascopes]

No description provided.

[github-actions]

Test Results

   385 files  ±0     385 suites  ±0   57m 18s ⏱️ + 3m 52s
8 835 tests ±0  8 759 ✔️ ±0  76 💤 ±0  0 ❌ ±0 
8 989 runs  ±0  8 913 ✔️ ±0  76 💤 ±0  0 ❌ ±0 

Results for commit 45af8c7. ± Comparison against base commit 49d48e5.

[codecov-commenter]

Codecov Report

Merging #113 (45af8c7) into main (49d48e5) will decrease coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #113      +/-   ##
==========================================
- Coverage   53.01%   52.97%   -0.04%     
==========================================
  Files          69       69              
  Lines        2522     2520       -2     
  Branches      230      229       -1     
==========================================
- Hits         1337     1335       -2     
  Misses       1090     1090              
  Partials       95       95              

Impacted Files	Coverage Δ
.../ascopes/jct/compilers/javac/JavacFlagBuilder.java	85.29% <100.00%> (-0.82%)	⬇️

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[sonatype-lift]

⚠️ 3 God Classes were detected by Lift in this project. Visit the Lift web console for more details.