fftw hangs on raspberry pi3

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Currently fftw does not work on my raspberry pi3. It hangs in a loop doing calls to clock_gettime:

clock_gettime(CLOCK_SGI_CYCLE, 0x7ea42558) = -1 EINVAL (Invalid argument)
clock_gettime(CLOCK_SGI_CYCLE, 0x7ea42558) = -1 EINVAL (Invalid argument)
clock_gettime(CLOCK_REALTIME, {tv_sec=1513978172, tv_nsec=339522337}) = 0
clock_gettime(CLOCK_REALTIME, {tv_sec=1513978172, tv_nsec=339672025}) = 0
clock_gettime(CLOCK_SGI_CYCLE, 0x7ea42558) = -1 EINVAL (Invalid argument)

The call clock_gettime(CLOCK_SGI_CYCLE, &t) from function getticks() fails with EINVAL. See : http://elixir.free-electrons.com/linux/latest/source/include/uapi/linux/time.h#L62 - "The driver implementing this got removed. The clock ID is kept as a place holder. Do not reuse!"

There was a commit preventing the usage of CLOCK_SGI_CYCLE on ANDROID. It should probably not be used on plain linux too.

I discussed this here: https://github.com/FFTW/fftw3/commit/950b153910f7f0dde9cc20cddeee5dc9048d25b7

I will add a pull request based on https://github.com/SETIguy comment https://github.com/FFTW/fftw3/commit/950b153910f7f0dde9cc20cddeee5dc9048d25b7#commitcomment-26583436

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See https://github.com/FFTW/fftw3/pull/123