add a fortified implementation of getcwd

Change-Id: Ice3e6d3e1ff07788305dc85f8ee4059baad5fac4
diff --git a/tests/fortify_compilation_test.cpp b/tests/fortify_compilation_test.cpp
index 166e8d9..072006e 100644
--- a/tests/fortify_compilation_test.cpp
+++ b/tests/fortify_compilation_test.cpp
@@ -262,3 +262,11 @@
   // clang should emit a warning, but doesn't
   fwrite(buf, 1, 5, stdout);
 }
+
+void test_getcwd() {
+  char buf[4];
+  // NOLINTNEXTLINE(whitespace/line_length)
+  // GCC: error: call to '__getcwd_dest_size_error' declared with attribute error: getcwd called with size bigger than destination
+  // clang should emit a warning, but doesn't
+  getcwd(buf, 5);
+}