Consider the following directory structure:

A/
  node_modules/
    ts-node/
    typescript-to-lua/
  plugin.ts
B/
  tsconfig.json

B/tsconfig.json contains a reference ../A/plugin.ts.

Before this change, running npx tstl -p ../B/tsconfig.json would correctly resolve node_modules/typescript-to-lua, then correctly resolve plugin.ts, but then claim ts-node is not installed, even though it is right there in node_modules/ts-node.

This change makes tstl try to resolve ts-node relative to tstl's location, rather than relative to the location of whatever is being translated.