Speed up time stretching ~3x on Linux with FFTW3. #1178

Job	Run time
Lint C++	17m 18s
Pre-build on ubuntu-20.04 with clang	1m 39s
Pre-build on macos-13 with clang	1m 13s
Lint Python (3.12, ubuntu-20.04)	9s
Pre-build on ubuntu-20.04 with gcc	1m 54s
Test with Python 3.7 + Address Sanitizer	7m 39s
Test with Python 3.8 + Address Sanitizer	8m 0s
Test with Python 3.9 + Address Sanitizer	7m 47s
Test with Python 3.10 + Address Sanitizer	7m 54s
Test with Python 3.11 + Address Sanitizer	7m 53s
Test 1 / 8 with Python 3.12 on ubuntu-20.04	1m 12s
Test with Python 3.7 on macos-13	2m 22s
Test 2 / 8 with Python 3.12 on ubuntu-20.04	1m 16s
Test with Python 3.8 on macos-13	2m 22s
Test 3 / 8 with Python 3.12 on ubuntu-20.04	1m 9s
Test with Python 3.9 on macos-13	2m 22s
Test 4 / 8 with Python 3.12 on ubuntu-20.04	1m 23s
Test with Python 3.10 on macos-13	2m 24s
Test 5 / 8 with Python 3.12 on ubuntu-20.04	1m 36s
Test with Python 3.11 on macos-13	2m 16s
Test 6 / 8 with Python 3.12 on ubuntu-20.04	1m 11s
Test with Python 3.12 on macos-13	2m 22s
Test 7 / 8 with Python 3.12 on ubuntu-20.04	1m 29s
Test with Python 3.7 on ubuntu-20.04	2m 13s
Test 8 / 8 with Python 3.12 on ubuntu-20.04	1m 30s
Test with Python 3.8 on ubuntu-20.04	2m 22s
Test with Python 3.9 on ubuntu-20.04	2m 25s
Test with Python 3.10 on ubuntu-20.04	2m 15s
Test with Python 3.11 on ubuntu-20.04	2m 11s
Test with Python 3.12 on ubuntu-20.04	2m 23s
Test with Python 3.12 on windows-latest	2m 2s
Build wheel for ${{ matrix.build }}	0s
Upload wheels to PyPI	0s
	1h 42m 11s

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