graphics/vulkan-validation-layers: Remove USE_LDCONFIG

USE_LDCONFIG shouldn't be necessary as Vulkan layers are not regular
libraries i.e., can only be used through libvulkan.so. For example,
vulkan-validation-layers, vulkan-extension-layer and layers from
mesa-devel all define the same symbols thus will create ambiguity if
not used via dlopen(3).

PR: 288141
Reported by: jbeich