Fix debug build when spirv-tools is not available
Fix debug build when spirv-tools is not available

vk::validateSpirV signature mismatch was causing linking error
in debug builds when DEQP_HAVE_SPIRV_TOOLS was not defined.

Change-Id: Icf98f80b72dfa744c4482b1abb0b7d1132aad296

KhronosGroup/VK-GL-CTS,googlestadia/VK-GL-CTS,KhronosGroup/Vulkan-CTS,googlestadia/VK-GL-CTS,googlestadia/VK-GL-CTS,KhronosGroup/Vulkan-CTS,googlestadia/VK-GL-CTS,chadversary/deqp,KhronosGroup/VK-GL-CTS,chadversary/deqp,googlestadia/VK-GL-CTS,chadversary/deqp,KhronosGroup/Vulkan-CTS,chadversary/deqp,KhronosGroup/VK-GL-CTS,KhronosGroup/VK-GL-CTS,chadversary/deqp,KhronosGroup/VK-GL-CTS,KhronosGroup/Vulkan-CTS,googlestadia/VK-GL-CTS,KhronosGroup/VK-GL-CTS,KhronosGroup/Vulkan-CTS,KhronosGroup/Vulkan-CTS,chadversary/deqp