Build Observatory as part of runtime

tools/build.py

Index: tools/build.py
diff --git a/tools/build.py b/tools/build.py
index b87084eb283607d543e62d964d885be763c0cca3..ec0646bb1414484beff8a7ea6fd5e36e80c182da 100755
--- a/tools/build.py
+++ b/tools/build.py
@@ -76,6 +76,11 @@ def BuildOptions():
       help='Name of the devenv.com/msbuild executable on Windows (varies for '
            'different versions of Visual Studio)',
       default=vs_executable)
+  result.add_option("--use-bootstrap-for-observatory",
+      help='Use a stripped down Dart binary built on the host machine '
+           'for building Observatory. Necessary on Linux machines which have '
+           'libc incompatibilities with the prebuilt Dart binaries.',
+      default=False, action="store_true")
   return result
 
 
@@ -361,7 +366,7 @@ def NotifyBuildDone(build_config, success, start):
       icon = 'info'
     else:
       icon = 'error'
-    command = ("powershell -command \"" 
+    command = ("powershell -command \""
       "[reflection.assembly]::loadwithpartialname('System.Windows.Forms')"
         "| Out-Null;"
       "[reflection.assembly]::loadwithpartialname('System.Drawing')"
@@ -384,6 +389,8 @@ def BuildOneConfig(options, target, target_os, mode, arch, override_tools):
   global filter_xcodebuild_output
   start_time = time.time()
   os.environ['DART_BUILD_MODE'] = mode
+  if options.use_bootstrap_for_observatory != False:
+    os.environ['DART_USE_BOOTSTRAP_BIN'] = '1'
   build_config = utils.GetBuildConf(mode, arch, target_os)
   if HOST_OS == 'macos':
     filter_xcodebuild_output = True