fix: do not exclude /path/ from process.env copying

Previously, we were forcing only the "canonical" env.Path on windows or
env.PATH on Unix.  However, msysgit bash uses env.PATH instead of
env.Path.

The result was that either the system path wasn't loaded (so binaries
like 'npm' couldn't be found in windows bash) or the local node_modules
paths weren't loaded (in windows cmd.exe, depending on environment
variable key order).  And, since they weren't being copied to the
object, the mergePath logic had no effect.

Author: isaacs

index.js

@@ -388,7 +388,7 @@ function makeEnv (data, opts, prefix, env) {
   if (!env) {
     env = {}
     for (var i in process.env) {
-      if (!i.match(/^npm_/) && (!i.match(/^PATH$/i) || i === PATH)) {
+      if (!i.match(/^npm_/)) {
         env[i] = process.env[i]
       }
     }