fix: webpack absolute output path

[ekoeryanto]

Summary

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• Bugfix
• Feature
• Code style update
• Refactor
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• No

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The PR fulfills these requirements:

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Other information:

[ulivz]

Since I don't use windows, so could you log the before/after resolving result so that I can know whether I can approve it?

BTW, I think using upath shouldn't take errors in windows.

[ekoeryanto]

@ulivz, so we need appveyor here.
here the log from my forked vuepress
before:
https://ci.appveyor.com/project/ekoeryanto/vuepress/build/job/w159tutdupa997nv
after:
https://ci.appveyor.com/project/ekoeryanto/vuepress/build/job/ll6oiqa4lk52y48x

as seen on the 'after' log line 49 and 50 I think the main issue is upath

[mAKEkr]

@ulivz upath is problem on webpack path detection.
webpack/webpack#66

[ekoeryanto]

@ulivz I think this is an urgent issue for windows users.
I'm afraid we need to revert 19e73d7 for safety reason

[meteorlxy]

BTW, I suggest to use exact version requirement for alpha/beta releases, so we can revert to the exact version quickly.

i.e.

  "dependencies": {
    "@vuepress/cli": "^1.0.0-alpha.5",  // ^1.0.0-alpha.5 => 1.0.0-alpha.5
    "@vuepress/core": "^1.0.0-alpha.5",  // ^1.0.0-alpha.5 => 1.0.0-alpha.5
    "@vuepress/theme-default": "^1.0.0-alpha.5"  // ^1.0.0-alpha.5 => 1.0.0-alpha.5
  },

[ekoeryanto]

It is fixed by d89f766

but after I reread the source, I think the better place to fix the issue is here

Sorry 😄