relesetools: Support running all the unittests with atest.

All the unittests will be built into releasetools_test. One can run the
tests with `atest releasetools_test` or the traditional way
`test_utils.py`. The atest way is recommended, which additionally builds
the required tools.

With the current support in Soong, we can't pack the built tools into
releasetools_test yet. So running `releasetools_test` alone in clound
would fail. Follow-up CLs will address the issue in order to deploy the
tests with TEST_MAPPING.

Bug: 112080715
Test: `atest releasetools_test`
Change-Id: Ica95517a5ab326f4e58fc57c6c2c276cfe882f3c

tools/releasetools/test_utils.py

@@ -1,3 +1,4 @@
+#!/usr/bin/env python
 #
 # Copyright (C) 2018 The Android Open Source Project
 #
@@ -40,6 +41,19 @@ def get_testdata_dir():
 
 def get_search_path():
   """Returns the search path that has 'framework/signapk.jar' under."""
+
+  def signapk_exists(path):
+    signapk_path = os.path.realpath(
+        os.path.join(path, 'framework', 'signapk.jar'))
+    return os.path.exists(signapk_path)
+
+  # Try with ANDROID_BUILD_TOP first.
+  full_path = os.path.realpath(os.path.join(
+      os.environ.get('ANDROID_BUILD_TOP', ''), 'out', 'host', 'linux-x86'))
+  if signapk_exists(full_path):
+    return full_path
+
+  # Otherwise try going with relative pathes.
   current_dir = os.path.dirname(os.path.realpath(__file__))
   for path in (
       # In relative to 'build/make/tools/releasetools' in the Android source.
@@ -47,9 +61,7 @@ def get_search_path():
       # Or running the script unpacked from otatools.zip.
       ['..']):
     full_path = os.path.realpath(os.path.join(current_dir, *path))
-    signapk_path = os.path.realpath(
-        os.path.join(full_path, 'framework', 'signapk.jar'))
-    if os.path.exists(signapk_path):
+    if signapk_exists(full_path):
       return full_path
   return None
 
@@ -123,3 +135,10 @@ class ReleaseToolsTestCase(unittest.TestCase):
 
   def tearDown(self):
     common.Cleanup()
+
+
+if __name__ == '__main__':
+  testsuite = unittest.TestLoader().discover(
+      os.path.dirname(os.path.realpath(__file__)))
+  # atest needs a verbosity level of >= 2 to correctly parse the result.
+  unittest.TextTestRunner(verbosity=2).run(testsuite)