Increase LLVM inline-threshold to 5000

[peterzhu2118]

Compared to the default of 225, this gives noticeable performance improvements.

For the following benchmark:

objs = []
2_000_000.times { objs << Object.new }

We can see this branch is about 10% faster:

Benchmark 1: branch
  Time (mean ± σ):     193.0 ms ±   3.3 ms    [User: 207.0 ms, System: 79.2 ms]
  Range (min … max):   189.1 ms … 203.1 ms    15 runs

Benchmark 2: master
  Time (mean ± σ):     214.9 ms ±   4.9 ms    [User: 245.2 ms, System: 79.5 ms]
  Range (min … max):   206.4 ms … 220.4 ms    13 runs

Summary
  branch ran
    1.11 ± 0.03 times faster than master