Refine sysprop_library header rules

Instead of unreliable giant if clause, it's enough to check dependency
between platform (system, system-ext), product, and vendor.

Test: sysprop_test soong test
Test: link against host_supported sysprop_library and use internal props
Change-Id: I7bd5df00b302fa261eff5120106aacc3df93c1b2