Fix libbase file.Readlink test on marlin/sailfish.

Bug: http://b/33306057
Test: ran tests
Change-Id: Ie6797e71d3507572da66d6b6966f8ee9373124a4

base/file_test.cpp

@@ -134,7 +134,11 @@ TEST(file, Readlink) {
   // Linux doesn't allow empty symbolic links.
   std::string min("x");
   // ext2 and ext4 both have PAGE_SIZE limits.
-  std::string max(static_cast<size_t>(4096 - 1), 'x');
+  // If file encryption is enabled, there's extra overhead to store the
+  // size of the encrypted symlink target. There's also an off-by-one
+  // in current kernels (and marlin/sailfish where we're seeing this
+  // failure are still on 3.18, far from current). http://b/33306057.
+  std::string max(static_cast<size_t>(4096 - 2 - 1 - 1), 'x');
 
   TemporaryDir td;
   std::string min_path{std::string(td.path) + "/" + "min"};