configure.ac: Fix HAVE_SNDIO_H handling #32

Job	Run time
build (ubuntu-gcc-autotools)	1m 36s
build (ubuntu-clang-autotools)	2m 26s
build (ubuntu-gcc-ossfuzz)	2m 12s
build (macos-autotools)	1m 21s
build (ubuntu-gcc-cmake)	43s
build (ubuntu-gcc-cmake-shared)	29s
build (ubuntu-clang-cmake)	50s
build (ubuntu-clang-cmake-shared)	37s
build (macos-cmake)	48s
build (macos-cmake-shared)	33s
build (windows-vs2022-x64)	8m 24s
build (windows-vs2022-x64-shared)	6m 19s
build (windows-vs2022-Win32)	7m 37s
build (windows-vs2022-Win32-shared)	6m 54s
	40m 49s

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