update building instructions #65

Job	Run time
Linux build (openblas)	5m 58s
Linux build (mkl)	6m 20s
Linux build (openblas / static)	6m 9s
Windows build (mkl)	4m 44s
Mac build (accelerate)	2m 40s
Windows build (openblas)	5m 6s
Windows build openblas installed (mkl)	4m 51s
Mac build (accelerate / static)	4m 13s
	40m 1s

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