Add support for building the Dart VM for Android OS.

tools/build.py

Index: tools/build.py
diff --git a/tools/build.py b/tools/build.py
index 1d1b8c805eb612d53389e92c512eeb5369442e54..be32e5c7afbb5460e3cef6d6d1253acc3c2d6970 100755
--- a/tools/build.py
+++ b/tools/build.py
@@ -29,6 +29,8 @@ def BuildOptions():
       help='Target architectures (comma-separated).',
       metavar='[all,ia32,x64,simarm,arm]',
       default=utils.GuessArchitecture())
+  result.add_option("--toolchainprefix",
+      help='Target toolchain prefix')
   result.add_option("-j",
       help='The number of parallel jobs to run.',
       metavar=HOST_CPUS,
@@ -57,7 +59,7 @@ def ProcessOptions(options):
   return True
 
 
-def setTools(arch):
+def setTools(arch, toolchainprefix):
   if arch == 'arm':
     toolsOverride = {
       "CC"  :  armcompilerlocation + "/bin/arm-none-linux-gnueabi-gcc",
@@ -67,7 +69,15 @@ def setTools(arch):
       "NM"  :  armcompilerlocation + "/bin/arm-none-linux-gnueabi-nm",
     }
     return toolsOverride
-
+  if toolchainprefix:
+    toolsOverride = {
+      "CC"  :  toolchainprefix + "-gcc",
+      "CXX" :  toolchainprefix + "-g++",
+      "AR"  :  toolchainprefix + "-ar",
+      "LINK":  toolchainprefix + "-g++",
+      "NM"  :  toolchainprefix + "-nm",
+    }
+    return toolsOverride
 
 def Execute(args):
   print "#" + ' '.join(args)
@@ -149,7 +159,7 @@ def Main():
 
         args += [target]
 
-      toolsOverride = setTools(arch)
+      toolsOverride = setTools(arch, options.toolchainprefix)
       if toolsOverride:
         for k, v in toolsOverride.iteritems():
           args.append(  k + "=" + v)