fix: Always normalize relative transform paths (#2096)

Author: mooooooi

NOTICE

@@ -43,6 +43,7 @@ under the licensing terms detailed in LICENSE:
 * Joe Pea <trusktr@gmail.com>
 * Felipe Gasper <FGasper@users.noreply.github.com>
 * Congcong Cai <77575210+HerrCai0907@users.noreply.github.com>
+* mooooooi <emwings@outlook.com>
 
 Portions of this software are derived from third-party works licensed under
 the following terms:

cli/util/options.js

@@ -237,6 +237,16 @@ function merge(config, currentOptions, parentOptions, parentBaseDir) {
 
 exports.merge = merge;
 
+function normalizePath(p) {
+  const parsed = path.parse(p);
+  if (!parsed.root) {
+    parsed.root = "./";
+  }
+  return path.format(parsed);
+}
+
+exports.normalizePath = normalizePath;
+
 const dynrequire = typeof __webpack_require__ === "function"
   ? __non_webpack_require__
   : require;
@@ -247,7 +257,7 @@ function resolvePath(p, baseDir, useNodeResolution = false) {
   if (useNodeResolution && !p.startsWith(".")) {
     return dynrequire.resolve(p, { paths: [ baseDir ] });
   }
-  return path.join(baseDir, p);
+  return normalizePath(path.join(baseDir, p));
 }
 
 exports.resolvePath = resolvePath;