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/getcwd_test.cpp b/tests/getcwd_test.cpp
index 791ffae..97b1d4f 100644
--- a/tests/getcwd_test.cpp
+++ b/tests/getcwd_test.cpp
@@ -51,7 +51,7 @@
 }
 
 TEST(getcwd, auto_too_large) {
-  SKIP_WITH_HWASAN; // allocation size too large
+  SKIP_WITH_HWASAN << "allocation size too large";
   // If we ask the library to allocate an unreasonably large buffer, ERANGE.
   errno = 0;
   char* cwd = getcwd(nullptr, static_cast<size_t>(-1));