tests: fix cmake and testrunner

App was writing to a TextView not on UI thread.

Fixes #318
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 61ba7bc..5a99442 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -1,7 +1,10 @@
 cmake_minimum_required(VERSION 3.4.1)
 
 # TODO: Remove this line and inherit it from the host environment
-set(ANDROID_NDK $ENV{HOME}/Library/Android/sdk/ndk-bundle)
+# This may work on Mac OS.
+# set(ANDROID_NDK $ENV{HOME}/Library/Android/sdk/ndk-bundle)
+# This may work on Linux.
+# set(ANDROID_NDK $ENV{HOME}/Android/sdk/ndk-bundle)
 
 # Include GoogleTest library
 set(GOOGLETEST_ROOT ${ANDROID_NDK}/sources/third_party/googletest)
diff --git a/tests/UnitTestRunner/app/src/main/java/com/google/oboe/tests/unittestrunner/MainActivity.java b/tests/UnitTestRunner/app/src/main/java/com/google/oboe/tests/unittestrunner/MainActivity.java
index b0e2d08..802faaf 100644
--- a/tests/UnitTestRunner/app/src/main/java/com/google/oboe/tests/unittestrunner/MainActivity.java
+++ b/tests/UnitTestRunner/app/src/main/java/com/google/oboe/tests/unittestrunner/MainActivity.java
@@ -105,8 +105,8 @@
 
             // read any errors from the attempted command
             while ((s = stdError.readLine()) != null) {
-                Log.d(TAG, "ERROR: " + s);
-                outputText.append("ERROR: " + s);
+                Log.e(TAG, "ERROR: " + s);
+                output.append("ERROR: " + s + "\n");
             }
 
             process.waitFor();