Fix Apple platform detection and iOS cross-build #2613

Job	Run time
xbuild-ios32	5m 38s
xbuild-ios	7m 7s
build-windows (cmake, gfortran, 0, 0)	37m 22s
build-windows (cmake, gfortran, 1, 0)	39m 44s
build-windows (make, gfortran, 0, 1)	8m 20s
build-windows (make, gfortran, 0, 0)	10m 55s
build-windows (make, gfortran, 1, 0)	7m 43s
build-windows (cmake, gfortran, 1, 1)	38m 16s
build-windows (cmake, gfortran, 0, 1)	37m 10s
build-windows (make, gfortran, 1, 1)	10m 6s
xbuild-x86_64	8m 28s
	3h 30m 49s

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