Resolve matcher path in single step

[bendrucker]

Resolves the path to matchers.json in a single call. When the parent directory is separately constructed, the compiler has to consider the possibility that any file within that directory will be loaded:

ncc: Version 0.27.0
ncc: Compiling file index.js
  0kB  dist/.github/matchers.json
  0kB  dist/.github/workflows/semver.yml
  2kB  dist/.github/workflows/test.yml
305kB  dist/index.js
307kB  [1020ms] - ncc 0.27.0

By resolving the actual path to the desired file, the compiler can copy that specific file only:

ncc: Version 0.27.0
ncc: Compiling file index.js
  0kB  dist/matchers.json
305kB  dist/index.js
305kB  [1077ms] - ncc 0.27.0

This reduces potential spurious build diffs, as seen in #21