Disable unity builds for targets with only one source file.

modules/CMakeLists.txt

@@ -77,6 +77,12 @@ macro(build_module SRC MODULE_SRC)
       PREFIX ""
       SUFFIX ""
     )
+    list(LENGTH MODULE_SRC MODULE_SRC_COUNT)
+    if(MODULE_SRC_COUNT LESS_EQUAL 1)
+      set_target_properties(${SO} PROPERTIES
+        UNITY_BUILD OFF
+      )
+    endif()
     add_dependencies(${SO} ${PROGRAM_NAME})
     if(HAVE_LOCALIZATION)
       add_dependencies(${SO} module_language)

vendor/CMakeLists.txt

@@ -14,6 +14,7 @@ foreach(LIBRARY IN LISTS LIBRARIES)
 			set_target_properties(${LIBRARY_TARGET} PROPERTIES
 				FOLDER "VendoredLibraries"
 				PREFIX ""
+				UNITY_BUILD OFF
 			)
 		endif()
 	endif()