Roll buildtools 0f8e6e4b12..cf8c4332f5

  In order to roll GN 4e73e432..6a9b6b43 (r367870:r370714) and pick up
  the following changes:

  65e89854 Allow .o files for GN generated inputs.
  d039a9f4 Remove enable_wifi_bootstrapping from doc
  b541f710 [gn] Fix typos in the documentation.
  8e5f41b2 tools/gn: delete generate_test_gn_data tool
  ff69eea6 Change cookbook to map target_arch to target_cpu
  21aff0d0 tools/gn: rename char_offset to column_number

TBR=dpranke@chromium.org
CQ_EXTRA_TRYBOTS=tryserver.chromium.mac:mac_chromium_gn_dbg;tryserver.chromium.win:win8_chromium_gn_dbg,win_chromium_gn_x64_rel

Review URL: https://codereview.chromium.org/1619683003

Cr-Commit-Position: refs/heads/master@{#370735}

DEPS

@@ -55,7 +55,7 @@ vars = {
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling build tools
   # and whatever else without interference from each other.
-  'buildtools_revision': '0f8e6e4b126ee88137930a0ae4776c4741808740',
+  'buildtools_revision': 'cf8c4332f5c9d0da4b4782d7f0122df74a16819b',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling PDFium
   # and whatever else without interference from each other.