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When building chrome on windows, tool-wrapper for linking is called 794 times.
And I found that calling python wrapper is relatively slow than calling link via ninja.

This CL replaces python wrapper to ninja wrapper to remove such overhead when we use lld.

I compared time of wrapper invocation using following powershell script.

for ($i = 0; $i -lt 100; $i++) {
    # ninja -t msvc -e environment.x64 -- C:/src/depot_tools/win_tools-2_7_6_bin/python/bin/python.exe -c ' '
    # python.exe ../../build/toolchain/win/tool_wrapper.py link-wrapper environment.x64 False C:/src/depot_tools/win_tools-2_7_6_bin/python/bin/python.exe -c ' ' # code for FlushFileBuffers is commented out.
}

* ninja wrapper, 7.451s for 100 invocation
* python wrapper, 17.803s for 100 invocation
Using ninja as env wrapper is more than 2 times faster.

Bug: 787903
Change-Id: I6531b59a6c43085782b0138a264ecfc9a6f65833
Reviewed-on: https://chromium-review.googlesource.com/1107678
Commit-Queue: Takuto Ikuta <tikuta@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#568836}