Revert "[BrowserSwitcher] Build BHO for both bitnesses"

This reverts commit 6c3a34bfc2030ffd304c54f5cb96d234622ef389.

Reason for revert: It broke some builds with:
The file:
  //out/Release_x64/win_clang_x86/browser_switcher_bho.dll.pdb
is listed as an input or source for the target:
  //chrome/browser/browser_switcher/bho:copy_browser_switcher_binaries
but no targets in the build generate that file.
See for instance https://ci.chromium.org/p/chromium/builders/ci/Jumbo%20Win%20x64/35757

and the comment in the bug.

Original change's description:
> [BrowserSwitcher] Build BHO for both bitnesses
> 
> To do so, this CL also adds support for the x86 toolchain in an x64
> build.
> 
> Instead of generating one DLL, we now generate 2 DLLs in the root
> out-dir:
> 
> - browser_switcher_bho.dll (x86)
> - browser_switcher_bho_64.dll (x64)
> 
> The one that is cross-built (i.e. bitness doesn't match the host) is
> built in a sub-directory, and then copied to the root out-dir.
> 
> Bug: 952897
> Change-Id: Ie96ff95556dbe41c8d8eb2fb5ce748964705e096
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1589457
> Reviewed-by: Bruce Dawson <brucedawson@chromium.org>
> Reviewed-by: Dirk Pranke <dpranke@chromium.org>
> Commit-Queue: Nicolas Ouellet-Payeur <nicolaso@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#663196}

TBR=thakis@chromium.org,dpranke@chromium.org,brucedawson@chromium.org,nicolaso@chromium.org

Change-Id: I2f1929a4e2ea2f9408273c5f04b52ee79580b4cc
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 952897
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1630427
Reviewed-by: Daniel Bratell <bratell@opera.com>
Commit-Queue: Daniel Bratell <bratell@opera.com>
Cr-Original-Commit-Position: refs/heads/master@{#663392}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: b0179d714f8129f2e95e447f35fc5c1031ffdb65
2 files changed