example/Makefile: adapt the include path selection from src/Makefile here

example/Makefile

@@ -5,7 +5,19 @@ CXX ?= g++
 
 TARGET = clfft_example
 
-CXXFLAGS += -O3 -Wall -g -I$(NVIDIA_SDK_INSTALL_PATH)/OpenCL/common/inc -I$(AMDAPPSDKROOT)/include -I../include
+ifndef OPENCL_INCLUDE
+ifdef CUDA_INSTALL_PATH
+OPENCL_INCLUDE = $(CUDA_INSTALL_PATH)/include
+endif
+ifdef OPENCL_INSTALL_PATH
+OPENCL_INCLUDE = $(OPENCL_INSTALL_PATH)/include
+endif
+endif
+ifndef OPENCL_INCLUDE
+OPENCL_INCLUDE = $(AMDAPPSDKROOT)/include -I$(NVIDIA_SDK_INSTALL_PATH)/OpenCL/common/inc
+endif
+
+CXXFLAGS += -O3 -Wall -g -I$(OPENCL_INCLUDE) -I../include -fPIC
 LDFLAGS += $(PWD)/../lib/libclfft.a
 
 OS = $(shell uname -s)