Setting Data_SOURCE_DIR requires that OGS_BUILD_TESTS is set already.

CMakeLists.txt

@@ -136,6 +136,11 @@ if(OGS_USE_EIGEN)
 	endif()
 endif()
 
+if(OGS_BUILD_TESTS)
+	set(Data_SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/Tests/Data CACHE INTERNAL "")
+	set(Data_BINARY_DIR ${CMAKE_CURRENT_BINARY_DIR}/Tests/Data CACHE INTERNAL "")
+endif()
+
 ######################
 ### Subdirectories ###
 ######################

scripts/cmake/SubmoduleSetup.cmake

@@ -14,8 +14,6 @@ set(REQUIRED_SUBMODULES
 )
 if(OGS_BUILD_TESTS)
 	list(APPEND REQUIRED_SUBMODULES Tests/Data)
-	set(Data_SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/Tests/Data CACHE INTERNAL "")
-	set(Data_BINARY_DIR ${CMAKE_CURRENT_BINARY_DIR}/Tests/Data CACHE INTERNAL "")
 endif()
 
 foreach(SUBMODULE ${REQUIRED_SUBMODULES})