[compiler-rt] [scudo] Test secondary cache options only if enabled (PR #95872)

[Fabio D'Urso via llvm-commits]

fabio-d wrote:

> I think the fix is legit but the test is specific to `DefaultConfig` , thus I'm wondering how is this failed on Fuchsia?

Because Fuchsia overrides it: [link](https://cs.opensource.google/fuchsia/fuchsia/+/main:zircon/system/ulib/c/scudo/custom_scudo_config.h;drc=9d216a2337d427077c508eff9443a0a90daa0814;l=10), [link](https://github.com/llvm/llvm-project/blob/5aaf2ab085ef85498a65a1af03a1b3812c2cf531/compiler-rt/lib/scudo/standalone/allocator_config.h#L46) and [link](https://cs.opensource.google/fuchsia/fuchsia/+/main:zircon/system/ulib/c/scudo/BUILD.gn;drc=b99197927f7dc996cf341132d87478c0e4a28c9b;l=100).

https://github.com/llvm/llvm-project/pull/95872