Merge pull request #2224 from small-yellow-duck/master

[build] check if CPU_ONLY is set when determining CUDA version

Makefile

@@ -232,6 +232,7 @@ endif
 # libstdc++ for NVCC compatibility on OS X >= 10.9 with CUDA < 7.0
 ifeq ($(OSX), 1)
 	CXX := /usr/bin/clang++
+	ifneq ($(CPU_ONLY), 1)
 		CUDA_VERSION := $(shell $(CUDA_DIR)/bin/nvcc -V | grep -o 'release \d' | grep -o '\d')
 		ifeq ($(shell echo $(CUDA_VERSION) \< 7.0 | bc), 1)
 			CXXFLAGS += -stdlib=libstdc++
@@ -239,6 +240,7 @@ ifeq ($(OSX), 1)
 		endif
 		# clang throws this warning for cuda headers
 		WARNINGS += -Wno-unneeded-internal-declaration
+	endif
 	# gtest needs to use its own tuple to not conflict with clang
 	COMMON_FLAGS += -DGTEST_USE_OWN_TR1_TUPLE=1
 	# boost::thread is called boost_thread-mt to mark multithreading on OS X