Revert of Force clang/tot bots to do clobber builds of clang for a bit.

tools/clang/scripts/update.py

 #!/usr/bin/env python
 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """This script is used to download prebuilt clang binaries.
 
 It is also used by package.py to build the prebuilt clang binaries."""
 
 import argparse
@@ skipping 465 matching lines @@
       cc = os.path.join(LLVM_BOOTSTRAP_INSTALL_DIR, 'bin', 'clang')
       cxx = os.path.join(LLVM_BOOTSTRAP_INSTALL_DIR, 'bin', 'clang++')
 
     if args.gcc_toolchain:
       # Tell the bootstrap compiler to use a specific gcc prefix to search
       # for standard library headers and shared object files.
       cflags = ['--gcc-toolchain=' + args.gcc_toolchain]
       cxxflags = ['--gcc-toolchain=' + args.gcc_toolchain]
     print 'Building final compiler'
 
-  # TODO(thakis): Remove this after a few hours.
-  if os.path.exists(LLVM_BUILD_DIR):
-    RmTree(LLVM_BUILD_DIR)
-
   if sys.platform == 'darwin':
     # Build libc++.dylib while some bots are still on OS X 10.6.
     libcxxbuild = os.path.join(LLVM_BUILD_DIR, 'libcxxbuild')
     if os.path.isdir(libcxxbuild):
       RmTree(libcxxbuild)
     libcxxflags = ['-O3', '-std=c++11', '-fstrict-aliasing']
 
     # libcxx and libcxxabi both have a file stdexcept.cpp, so put their .o files
     # into different subdirectories.
     os.makedirs(os.path.join(libcxxbuild, 'libcxx'))
@@ skipping 314 matching lines @@
     args.force_local_build = True
     if 'OS=android' not in os.environ.get('GYP_DEFINES', ''):
       # Only build the Android ASan rt on ToT bots when targetting Android.
       args.with_android = False
 
   return UpdateClang(args)
 
 
 if __name__ == '__main__':
   sys.exit(main())