Skip installation of UCRT

The UCRT is now optional and it failed to install on one builder.
Making optional to fix build break

If this doesn't fix the break on the waterfall then the switch
to VS 2015 will need to be reverted (crrev.com/1598493004).

TBR=scottmg@chromium.org
BUG=440500

Review URL: https://codereview.chromium.org/1680433002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@298634 0039d316-1c4b-4281-b951-d872f2087c98

win_toolchain/get_toolchain_if_necessary.py

@@ -354,36 +354,7 @@ def GetInstallerName():
 
 
 def InstallUniversalCRTIfNeeded(abs_target_dir):
-  installer_name = GetInstallerName()
-  if not installer_name:
-    return
-
-  bitness = platform.architecture()[0]
-  # When running 64-bit python the x64 DLLs will be in System32
-  x64_path = 'System32' if bitness == '64bit' else 'Sysnative'
-  x64_path = os.path.join(r'C:\Windows', x64_path)
-  sample_crt_file = os.path.join(x64_path, 'ucrtbase.dll')
-
-  if os.path.exists(sample_crt_file):
-    # Nothing to do.
-    return
-
-  print ('%s does not exist - installing Windows 10 Universal C Runtime' %
-         sample_crt_file)
-
-  installer = os.path.join(abs_target_dir, "installers", installer_name)
-  command = r'wusa.exe /quiet "%s"' % installer
-  print 'Running %s' % command
-
-  try:
-    subprocess.check_call(command)
-  # Trap OSError instead of WindowsError so pylint will succeed on Linux.
-  except OSError as e:
-    if e.winerror == 740: # The requested operation requires elevation
-      print 'Elevation required. You can manually install this update:'
-      print '  %s' % installer
-      return
-    raise e
+  return
 
 
 def main():