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/grp_pwd_file_test.cpp b/tests/grp_pwd_file_test.cpp
index 66866fb..adcdbd6 100644
--- a/tests/grp_pwd_file_test.cpp
+++ b/tests/grp_pwd_file_test.cpp
@@ -103,7 +103,7 @@
   EXPECT_FALSE(passwd_file.FindById(3, nullptr));
 
 #else   // __BIONIC__
-  GTEST_LOG_(INFO) << "This test does nothing.\n";
+  GTEST_SKIP() << "bionic-only test";
 #endif  // __BIONIC__
 }
 
@@ -123,7 +123,7 @@
   EXPECT_FALSE(group_file.FindById(3, nullptr));
 
 #else   // __BIONIC__
-  GTEST_LOG_(INFO) << "This test does nothing.\n";
+  GTEST_SKIP() << "bionic-only test";
 #endif  // __BIONIC__
 }
 
@@ -161,7 +161,7 @@
   EXPECT_FALSE(passwd_file.FindById(50, nullptr));
 
 #else   // __BIONIC__
-  GTEST_LOG_(INFO) << "This test does nothing.\n";
+  GTEST_SKIP() << "bionic-only test";
 #endif  // __BIONIC__
 }
 
@@ -197,7 +197,7 @@
   EXPECT_FALSE(group_file.FindById(799, nullptr));
 
 #else   // __BIONIC__
-  GTEST_LOG_(INFO) << "This test does nothing.\n";
+  GTEST_SKIP() << "bionic-only test";
 #endif  // __BIONIC__
 }
 
@@ -219,7 +219,7 @@
   FindAndCheckPasswdEntry(&passwd_file, "vendor_name", 3, 4, "dir", "shell");
 
 #else   // __BIONIC__
-  GTEST_LOG_(INFO) << "This test does nothing.\n";
+  GTEST_SKIP() << "bionic-only test";
 #endif  // __BIONIC__
 }
 
@@ -241,6 +241,6 @@
   FindAndCheckGroupEntry(&group_file, "vendor_name", 2);
 
 #else   // __BIONIC__
-  GTEST_LOG_(INFO) << "This test does nothing.\n";
+  GTEST_SKIP() << "bionic-only test";
 #endif  // __BIONIC__
 }