Symbol: Add presubmit testing

Add symbol's unit tests to presubmit.

Test: atest python-symbol_test
Change-Id: I37eb4151365507ab2a95d7789408504cca78153c

scripts/Android.bp

@@ -37,3 +37,13 @@ python_test_host {
     test_config: "native_heapdump_viewer-tests.xml",
     test_suites: ["general-tests"],
 }
+
+python_test_host {
+    name: "python-symbol_test",
+    main: "symbol.py",
+    // Would be nice to use the library above, but as it's single-source
+    // this doesn't work.
+    srcs: ["symbol.py"],
+    test_config: "symbol-tests.xml",
+    test_suites: ["general-tests"],
+}

scripts/TEST_MAPPING

@@ -2,6 +2,9 @@
   "presubmit": [
     {
       "name": "python-native_heapdump_viewer_test"
+    },
+    {
+      "name": "python-symbol_test"
     }
   ]
 }

scripts/symbol-tests.xml

@@ -0,0 +1,7 @@
+<configuration description="Config for python tradefed symbol test">
+    <option name="test-suite-tag" value="python-symbol_test" />
+    <test class="com.android.tradefed.testtype.python.PythonBinaryHostTest" >
+        <option name="par-file-name" value="python-symbol_test" />
+        <option name="test-timeout" value="2m" />
+    </test>
+</configuration>

scripts/symbol.py

@@ -28,8 +28,11 @@ import signal
 import subprocess
 import unittest
 
-ANDROID_BUILD_TOP = str(os.environ["ANDROID_BUILD_TOP"])
-if not ANDROID_BUILD_TOP:
+try:
+  ANDROID_BUILD_TOP = str(os.environ["ANDROID_BUILD_TOP"])
+  if not ANDROID_BUILD_TOP:
+    ANDROID_BUILD_TOP = "."
+except:
   ANDROID_BUILD_TOP = "."
 
 def FindSymbolsDir():
@@ -550,6 +553,7 @@ class FindToolchainTests(unittest.TestCase):
     ARCH = abi
     FindToolchain() # Will throw on failure.
 
+  @unittest.skipIf(ANDROID_BUILD_TOP == '.', 'Test only supported in an Android tree.')
   def test_toolchains_found(self):
     self.assert_toolchain_found("arm")
     self.assert_toolchain_found("arm64")