[NaCl SDK] Fix build_sdk to prepare for turning on pyauto example testing.

native_client_sdk/src/build_tools/buildbot_common.py

Index: native_client_sdk/src/build_tools/buildbot_common.py
diff --git a/native_client_sdk/src/build_tools/buildbot_common.py b/native_client_sdk/src/build_tools/buildbot_common.py
index e1e29ddbddc7cbbab586dcdefc8bfb1107814f58..5275cd4ad8548ad930da1247f1a833402c62daf4 100644
--- a/native_client_sdk/src/build_tools/buildbot_common.py
+++ b/native_client_sdk/src/build_tools/buildbot_common.py
@@ -18,6 +18,22 @@ sys.path.append(os.path.join(SDK_SRC_DIR, 'tools'))
 
 import oshelpers
 
+def IsSDKBuilder():
+  """Returns True if this script is running on an SDK builder.
+
+  False means it is either running on a trybot, or a user's machine.
+
+  Trybot names:
+    naclsdkm-((pnacl-)?linux|mac|windows(32|64))
+
+  Builder names:
+    (pnacl-)?(windows|mac|linux)-sdk-multi(rel)?
+
+    except there are currently no pnacl multirel bots, and
+    pnacl-windows-sdk-multi is actually called pnacl-win-sdk-multi."""
+  return '-sdk-multi' in os.getenv('BUILDBOT_BUILDERNAME', '')
+
+
 def ErrorExit(msg):
   """Write and error to stderr, then exit with 1 signaling failure."""
   sys.stderr.write(msg + '\n')