win: Let reorder-imports.py fail if its invocation of swapimport.exe fails.
win: Let reorder-imports.py fail if its invocation of swapimport.exe fails.

At first I didn't hook up the script correctly in the gn build.  swapimport.exe
printed

  ERROR:swapimport_app.cc(214)] Path does not exist: ../../chrome/initialexe\chrome.exe

but that didn't make the build fail -- instead, it silently left the old
chrome.exe (from prior builds) around.  Make it so that swapimport.exe failing
makes the build fail.

BUG=505062, 512599

Review URL: https://codereview.chromium.org/1363243002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#350482}

axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk