fix robin-hood-hashing detection

Index: CMakeLists.txt
--- CMakeLists.txt.orig
+++ CMakeLists.txt
@@ -167,6 +167,7 @@ if(UNIX AND NOT APPLE) # i.e. Linux
 
     if(BUILD_WSI_XCB_SUPPORT)
         find_package(XCB REQUIRED)
+        include_directories(${XCB_INCLUDE_DIR})
     endif()
 
     if(BUILD_WSI_XLIB_SUPPORT)
@@ -251,9 +252,10 @@ option(BUILD_LAYERS "Build layers" ON)
 option(BUILD_LAYER_SUPPORT_FILES "Generate layer files" OFF) # For generating files when not building layers
 option(USE_ROBIN_HOOD_HASHING "Use robin-hood-hashing" ON)
 if (USE_ROBIN_HOOD_HASHING)
-    if (NOT TARGET robin_hood::robin_hood)
-        find_package(robin_hood REQUIRED CONFIG)
+    if(NOT ROBIN_HOOD_HASHING_INSTALL_DIR)
+        set(ROBIN_HOOD_HASHING_INSTALL_DIR $ENV{ROBIN_HOOD_HASHING_INSTALL_DIR} PATH "Path to robin-hood-hashing repository")
     endif()
+    set(ROBIN_HOOD_HASHING_INCLUDE_DIR "${ROBIN_HOOD_HASHING_INSTALL_DIR}/src/include" PATH "Path to robin-hood-hashing/src/include")
 endif()
 
 if(BUILD_LAYERS OR BUILD_TESTS)
@@ -383,7 +385,7 @@ target_include_directories(VkLayer_utils
                                   ${VulkanHeaders_INCLUDE_DIR})
 
 if (USE_ROBIN_HOOD_HASHING)
-    target_link_libraries(VkLayer_utils PUBLIC robin_hood::robin_hood)
+    target_include_directories(VkLayer_utils PUBLIC ${ROBIN_HOOD_HASHING_INCLUDE_DIR})
     target_compile_definitions(VkLayer_utils PUBLIC USE_ROBIN_HOOD_HASHING)
 endif()
 
