Workaround PATH casing issues on Windows

lib/testing-utils.js

@@ -64,6 +64,13 @@ function setupTests(test) {
         const processStderrWrite = process.stderr.write.bind(process.stderr);
         t.context.stderrWrite = processStderrWrite;
         process.stderr.write = wrapOutput(t.context);
+        // Workaround an issue in tests where the case insensitivity of the `$PATH`
+        // environment variable on Windows isn't preserved, i.e. `process.env.PATH`
+        // is not the same as `process.env.Path`.
+        const pathKeys = Object.keys(process.env).filter((k) => k.toLowerCase() === "path");
+        if (pathKeys.length > 0) {
+            process.env.PATH = process.env[pathKeys[0]];
+        }
         // Many tests modify environment variables. Take a copy now so that
         // we reset them after the test to keep tests independent of each other.
         // process.env only has strings fields, so a shallow copy is fine.