fs: improve globSync performance

[Trott]

Benchmark results:

                                                                                    confidence improvement accuracy (*)   (**)  (***)
fs/bench-glob.js recursive='false' mode='async' pattern='*.js' dir='lib' n=1000                    -0.28 %       ±2.63% ±3.50% ±4.56%
fs/bench-glob.js recursive='false' mode='async' pattern='**/*' dir='lib' n=1000                     0.15 %       ±2.85% ±3.81% ±4.98%
fs/bench-glob.js recursive='false' mode='async' pattern='**/**.js' dir='lib' n=1000                -1.03 %       ±2.85% ±3.79% ±4.94%
fs/bench-glob.js recursive='false' mode='sync' pattern='*.js' dir='lib' n=1000                     -0.49 %       ±1.39% ±1.86% ±2.42%
fs/bench-glob.js recursive='false' mode='sync' pattern='**/*' dir='lib' n=1000               *      0.82 %       ±0.68% ±0.91% ±1.19%
fs/bench-glob.js recursive='false' mode='sync' pattern='**/**.js' dir='lib' n=1000         ***      1.38 %       ±0.73% ±0.98% ±1.29%
fs/bench-glob.js recursive='true' mode='async' pattern='*.js' dir='lib' n=1000                      0.31 %       ±2.33% ±3.09% ±4.03%
fs/bench-glob.js recursive='true' mode='async' pattern='**/*' dir='lib' n=1000                     -0.90 %       ±3.45% ±4.59% ±5.98%
fs/bench-glob.js recursive='true' mode='async' pattern='**/**.js' dir='lib' n=1000                  0.26 %       ±2.46% ±3.28% ±4.26%
fs/bench-glob.js recursive='true' mode='sync' pattern='*.js' dir='lib' n=1000                       0.01 %       ±0.92% ±1.23% ±1.60%
fs/bench-glob.js recursive='true' mode='sync' pattern='**/*' dir='lib' n=1000                       0.57 %       ±0.62% ±0.83% ±1.09%
fs/bench-glob.js recursive='true' mode='sync' pattern='**/**.js' dir='lib' n=1000           **      1.89 %       ±1.35% ±1.82% ±2.41%

Be aware that when doing many comparisons the risk of a false-positive result increases.
In this case, there are 12 comparisons, you can thus expect the following amount of false-positive results:
  0.60 false positives, when considering a   5% risk acceptance (*, **, ***),
  0.12 false positives, when considering a   1% risk acceptance (**, ***),
  0.01 false positives, when considering a 0.1% risk acceptance (***)