Broaden the search for native test files.

Previously we were looking for test files with this pattern: test_*
I added *_test.[cc|cpp] and *_unittest.[cc|cpp]

The search also scan all the subdirectories of the build_path from
the test definition.

I added a filtering stage where missing tests are ignored.
For instance we may have a source file that has not been built for
the target, in which case it is ignored when we run the target tests.

In android_build.py I added 4 helper functions to get access to the
build environment:
- GetHostBin
- GetProductOut
- GetTargetSystemBin
- GetHostOsArch

Replace all the hardcoded linux-x86 strings with the value returned
by GetHostOsArch.
diff --git a/testrunner/android_build.py b/testrunner/android_build.py
index ca43ece..976f2bb 100644
--- a/testrunner/android_build.py
+++ b/testrunner/android_build.py
@@ -3,22 +3,24 @@
 #
 # Copyright 2008, The Android Open Source Project
 #
-# Licensed under the Apache License, Version 2.0 (the "License"); 
-# you may not use this file except in compliance with the License. 
-# You may obtain a copy of the License at 
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
 #
-#     http://www.apache.org/licenses/LICENSE-2.0 
+#     http://www.apache.org/licenses/LICENSE-2.0
 #
-# Unless required by applicable law or agreed to in writing, software 
-# distributed under the License is distributed on an "AS IS" BASIS, 
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
-# See the License for the specific language governing permissions and 
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
 # limitations under the License.
 
 """Contains utility functions for interacting with the Android build system."""
 
 # Python imports
 import os
+import re
+import subprocess
 
 # local imports
 import errors
@@ -38,8 +40,96 @@
     AbortError: if Android build root could not be found.
   """
   # TODO: does this need to be reimplemented to be like gettop() in envsetup.sh
-  root_path = os.getenv('ANDROID_BUILD_TOP')
+  root_path = os.getenv("ANDROID_BUILD_TOP")
   if root_path is None:
-    logger.Log('Error: ANDROID_BUILD_TOP not defined. Please run envsetup.sh')
+    logger.Log("Error: ANDROID_BUILD_TOP not defined. Please run envsetup.sh")
     raise errors.AbortError
   return root_path
+
+
+def GetHostOsArch():
+  """Identify the host os and arch.
+
+  Returns:
+    The triple (HOST_OS, HOST_ARCH, HOST_OS-HOST_ARCH).
+
+  Raises:
+    AbortError: If the os and/or arch could not be found.
+  """
+  command = ("CALLED_FROM_SETUP=true BUILD_SYSTEM=build/core "
+             "make --no-print-directory -C \"%s\" -f build/core/config.mk "
+             "dumpvar-report_config") % GetTop()
+
+  # Use the shell b/c we set some env variables before the make command.
+  config = subprocess.Popen(command, stdout=subprocess.PIPE,
+                            shell=True).communicate()[0]
+  host_os = re.search("HOST_OS=(\w+)", config).group(1)
+  host_arch = re.search("HOST_ARCH=(\w+)", config).group(1)
+  if not (host_os and host_arch):
+    logger.Log("Error: Could not get host's OS and/or ARCH")
+    raise errors.AbortError
+  return (host_os, host_arch, "%s-%s" % (host_os, host_arch))
+
+
+def GetHostBin():
+  """Compute the full pathname to the host binary directory.
+
+  Typically $ANDROID_BUILD_TOP/out/host/linux-x86/bin.
+
+  Assumes build environment has been properly configured by envsetup &
+  lunch/choosecombo.
+
+  Returns:
+    The absolute file path of the Android host binary directory.
+
+  Raises:
+    AbortError: if Android host binary directory could not be found.
+  """
+  (_, _, os_arch) = GetHostOsArch()
+  path = os.path.join(GetTop(), "out", "host", os_arch, "bin")
+  if not os.path.exists(path):
+    logger.Log("Error: Host bin path could not be found %s" % path)
+    raise errors.AbortError
+  return path
+
+
+def GetProductOut():
+  """Returns the full pathname to the target/product directory.
+
+  Typically the value of the env variable $ANDROID_PRODUCT_OUT.
+
+  Assumes build environment has been properly configured by envsetup &
+  lunch/choosecombo.
+
+  Returns:
+    The absolute file path of the Android product directory.
+
+  Raises:
+    AbortError: if Android product directory could not be found.
+  """
+  path = os.getenv("ANDROID_PRODUCT_OUT")
+  if path is None:
+    logger.Log("Error: ANDROID_PRODUCT_OUT not defined. Please run envsetup.sh")
+    raise errors.AbortError
+  return path
+
+
+def GetTargetSystemBin():
+  """Returns the full pathname to the target/product system/bin directory.
+
+  Typically the value of the env variable $ANDROID_PRODUCT_OUT/system/bin
+
+  Assumes build environment has been properly configured by envsetup &
+  lunch/choosecombo.
+
+  Returns:
+    The absolute file path of the Android target system bin directory.
+
+  Raises:
+    AbortError: if Android target system bin directory could not be found.
+  """
+  path = os.path.join(GetProductOut(), "system", "bin")
+  if not os.path.exists(path):
+    logger.Log("Error: Target system bin path could not be found")
+    raise errors.AbortError
+  return path