Move build/ to build_gyp/.

DEPS

 use_relative_paths = True
 
 vars = {
   'chromium_git': 'https://chromium.googlesource.com',
   'pdfium_git': 'https://pdfium.googlesource.com',
 
   'buildtools_revision': 'c2f259809d5ede3275df5ea0842f0431990c4f98',
   'clang_revision': '9dc1904d214a77f081362c1b848b5f28d2192748',
   'cygwin_revision': 'c89e446b273697fadf3a10ff1007a97c0b7de6df',
   'gmock_revision': '29763965ab52f24565299976b936d1265cb6a271',
   'gtest_revision': '8245545b6dc9c4703e6496d1efd19e975ad2b038',
   'icu_revision': 'c291cde264469b20ca969ce8832088acb21e0c48',
   'pdfium_tests_revision': '7ef8719fac859e1d23d667d4c3038ae8b38e4d36',
   'skia_revision': '0a291c7b7eea1807bd58bdaa60c258fd0ebeb257',
   'trace_event_revision': 'd83d44b13d07c2fd0a40101a7deef9b93b841732',
   'v8_revision': '47bcec782b752ba411bd8bba6e390d1cc1c3226e',
 
 }
 
 deps = {
-  "build/gyp":
+  "build_gyp/gyp":
     Var('chromium_git') + "/external/gyp",
 
   "buildtools":
     Var('chromium_git') + "/chromium/buildtools.git@" + Var('buildtools_revision'),
 
   "testing/corpus":
     Var('pdfium_git') + "/pdfium_tests@" + Var('pdfium_tests_revision'),
 
   "testing/gmock":
     Var('chromium_git') + "/external/googlemock.git@" + Var('gmock_revision'),
@@ skipping 29 matching lines @@
   # Note: public is not here because core cannot depend on public.
   '+testing',
   '+third_party/base',
 ]
 
 hooks = [
   {
     # A change to a .gyp, .gypi, or to GYP itself should run the generator.
     'name': 'gyp',
     'pattern': '.',
-    'action': ['python', 'pdfium/build/gyp_pdfium'],
+    'action': ['python', 'pdfium/build_gyp/gyp_pdfium'],
   },
   # Pull GN binaries. This needs to be before running GYP below.
   {
     'name': 'gn_win',
     'pattern': '.',
     'action': [ 'download_from_google_storage',
                 '--no_resume',
                 '--platform=win32',
                 '--no_auth',
                 '--bucket', 'chromium-gn',
@@ skipping 56 matching lines @@
                 '-s', 'pdfium/buildtools/linux64/clang-format.sha1',
     ],
   },
   {
     # Pull clang if needed or requested via GYP_DEFINES.
     'name': 'clang',
     'pattern': '.',
     'action': ['python', 'pdfium/tools/clang/scripts/update.py', '--if-needed'],
   },
 ]