OS X linker does not like empty compilation unit by itself in a library. Scons creates one library (.a) per kernel. This fixes that

intern/cycles/kernel/kernel_sse2.cpp

@@ -71,4 +71,9 @@ void kernel_cpu_sse2_shader(KernelGlobals *kg, uint4 *input, float4 *output, int
 
 CCL_NAMESPACE_END
 
+#else
+
+/* needed for some linkers in combination with scons making empty compilation unit in a library */
+void __dummy_function_cycles_sse2(){}
+
 #endif

intern/cycles/kernel/kernel_sse3.cpp

@@ -72,5 +72,9 @@ void kernel_cpu_sse3_shader(KernelGlobals *kg, uint4 *input, float4 *output, int
 }
 
 CCL_NAMESPACE_END
+#else
+
+/* needed for some linkers in combination with scons making empty compilation unit in a library */
+void __dummy_function_cycles_sse3(){}
 
 #endif

intern/cycles/kernel/kernel_sse41.cpp

@@ -73,5 +73,9 @@ void kernel_cpu_sse41_shader(KernelGlobals *kg, uint4 *input, float4 *output, in
 }
 
 CCL_NAMESPACE_END
+#else
+
+/* needed for some linkers in combination with scons making empty compilation unit in a library */
+void __dummy_function_cycles_sse41(){}
 
 #endif