bionic tests: use GTEST_SKIP.

Also be a bit more to the point in our messages, focusing on "why" not
"what".

Test: ran tests
Change-Id: I297806c7a102bd52602dcd2fcf7a2cd34aba3a11
diff --git a/tests/wchar_test.cpp b/tests/wchar_test.cpp
index 9aef800..9b4fc4f 100644
--- a/tests/wchar_test.cpp
+++ b/tests/wchar_test.cpp
@@ -713,7 +713,7 @@
   ASSERT_EQ(nullptr, open_wmemstream(&p, nullptr));
   ASSERT_EQ(EINVAL, errno);
 #else
-  GTEST_LOG_(INFO) << "This test does nothing.\n";
+  GTEST_SKIP() << "This test is bionic-specific";
 #endif
 }