cmake: update FindFX module

cmake/FindFX.cmake

@@ -51,15 +51,7 @@ endif ()
 
 set(assemblies ${FX_FIND_COMPONENTS})
 set(required_vars)
-
+set(in_tree FALSE)
-if (NOT FX_INCLUDE_DIR)
-	find_path(FX_INCLUDE_DIR
-		NAMES fx/misc.h ${FX_FIND_ARGS}
-		PATH_SUFFIXES include
-		PATHS ${FX_SEARCH_PATHS})
-endif ()
-
-set(required_vars FX_INCLUDE_DIR)
 
 foreach (assembly ${assemblies})
 	string(TOLOWER ${assembly} header_name)
@@ -69,10 +61,15 @@ foreach (assembly ${assemblies})
 	set(lib_name ${assembly}${_lib_suffix})
 
 	if (NOT ${macro_name}_LIBRARY)
+		if (TARGET ${assembly})
+			set (${macro_name}_LIBRARY ${assembly})
+			set(in_tree TRUE)
+		else ()
 			find_library(${macro_name}_LIBRARY
 				NAMES ${lib_name} ${FX_FIND_ARGS}
 				PATH_SUFFIXES lib
 				PATHS ${FX_SEARCH_PATHS})
+		endif ()
 	else ()
 		# on Windows, ensure paths are in canonical format (forward slahes):
 		file(TO_CMAKE_PATH "${${macro_name}_LIBRARY}" ${macro_name}_LIBRARY)
@@ -81,6 +78,14 @@ foreach (assembly ${assemblies})
 	list(APPEND required_vars ${macro_name}_LIBRARY)
 endforeach (assembly)
 
+if (NOT FX_INCLUDE_DIR AND NOT in_tree)
+	list(APPEND required_vars FX_INCLUDE_DIR)
+	find_path(FX_INCLUDE_DIR
+		NAMES fx/misc.h ${FX_FIND_ARGS}
+		PATH_SUFFIXES include
+		PATHS ${FX_SEARCH_PATHS})
+endif ()
+
 unset(FX_FIND_ARGS)
 
 include(FindPackageHandleStandardArgs)
@@ -106,6 +111,9 @@ if (FX_FOUND)
 		set(lib_name ${assembly}${_lib_suffix})
 
 		if (NOT TARGET FX::${target_name})
+			if (TARGET ${assembly})
+				add_library(FX::${target_name} ALIAS ${assembly})
+			else ()
 				add_library(FX::${target_name} UNKNOWN IMPORTED)
 				set_target_properties(FX::${target_name} PROPERTIES
 					INTERFACE_INCLUDE_DIRECTORIES "${FX_INCLUDE_DIR}")
@@ -114,10 +122,10 @@ if (FX_FOUND)
 				if (FX_STATIC)
 					target_compile_definitions(FX::${target_name} INTERFACE FX_STATIC=1)
 				endif ()
-
 				set_target_properties(FX::${target_name} PROPERTIES
 					IMPORTED_LINK_INTERFACE_LANGUAGES "C"
 					IMPORTED_LOCATION "${${macro_name}_LIBRARY}")
+			endif ()
 			set(created_targets ${created_targets} ${assembly})
 		endif ()
 	endforeach (assembly)