Don't hardcode the source filename

In order to compile these tests with different CXXFLAGS, I needed to copy them
to different filenames to trick the compiler. Unfortunately, this triggers a
failure with one of the tests as it hardcodes the path to the test, instead of
relying on the compiler to fill in the path via `__FILE__`.

Using `__FILE__` is standard and works. Rely on it instead of a hardcoded path.

contrib/googletest/googletest/test/googletest-death-test_ex_test.cc

@@ -68,7 +68,7 @@ TEST(CxxExceptionDeathTest, PrintsMessageForStdExceptions) {
                           "exceptional message");
   // Verifies that the location is mentioned in the failure text.
   EXPECT_NONFATAL_FAILURE(EXPECT_DEATH(throw TestException(), ""),
-                          "googletest-death-test_ex_test.cc");
+                          __FILE__);
 }
 # endif  // GTEST_HAS_EXCEPTIONS