Configure an ignore pattern so jest will shut up

If the nodenv tarball (as downloaded by the tool-cache) lives in tmp/
along with the "cached" version, then jest's haste-map nonsense will
find duplicate package names and throw a warning. (Despite these
packages never being required!?!?)

Option: configure "modulePathIgnorePatterns": ["/tmp"] in package.json

Or: move the temp download cache out of the project

jestjs/jest#8114

installer.test.js

@@ -8,7 +8,7 @@ const path = require('path')
 const existsSync = require('fs').existsSync
 
 process.env.RUNNER_TOOL_CACHE = path.join(__dirname, '../tmp/runner_tools')
-process.env.RUNNER_TEMP = path.join(__dirname, '../tmp/runner_temp')
+process.env.RUNNER_TEMP = path.join(__dirname, '../tmp/runner_tmpdir')
 
 const installNodenv = require('./installer').installNodenv