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/stdio_ext_test.cpp b/tests/stdio_ext_test.cpp
index d84fda0..fce600a 100644
--- a/tests/stdio_ext_test.cpp
+++ b/tests/stdio_ext_test.cpp
@@ -193,7 +193,7 @@
 
 TEST(stdio_ext, __fseterr) {
 #if defined(__GLIBC__)
-  GTEST_LOG_(INFO) << "glibc doesn't have __fseterr, but gnulib will use it";
+  GTEST_SKIP() << "glibc doesn't have __fseterr, but gnulib will use it";
 #else
   FILE* fp = fopen("/dev/null", "w");