Add sndio support (#3715)

Add sndio support

cmake/Modules/FindSndio.cmake

@@ -0,0 +1,71 @@
+# Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+# file Copyright.txt or https://cmake.org/licensing for details.
+
+#[=======================================================================[.rst:
+FindSndio
+-------
+
+Finds the Sndio library.
+
+Imported Targets
+^^^^^^^^^^^^^^^^
+
+This module provides the following imported targets, if found:
+
+``Sndio::Sndio``
+  The Sndio library
+
+Result Variables
+^^^^^^^^^^^^^^^^
+
+This will define the following variables:
+
+``Sndio_FOUND``
+  True if the system has the Sndio library.
+``Sndio_VERSION``
+  The version of the Sndio library which was found.
+``Sndio_INCLUDE_DIRS``
+  Include directories needed to use Sndio.
+``Sndio_LIBRARIES``
+  Libraries needed to link to Sndio.
+
+Cache Variables
+^^^^^^^^^^^^^^^
+
+The following cache variables may also be set:
+
+``Sndio_INCLUDE_DIR``
+  The directory containing ``sndio.h``.
+``Sndio_LIBRARY``
+  The path to the Sndio library.
+
+#]=======================================================================]
+
+find_path(Sndio_INCLUDE_DIR sndio.h)
+find_library(Sndio_LIBRARY sndio)
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(Sndio
+  FOUND_VAR Sndio_FOUND
+  REQUIRED_VARS
+    Sndio_LIBRARY
+    Sndio_INCLUDE_DIR
+)
+
+if(Sndio_FOUND)
+  set(Sndio_LIBRARIES ${Sndio_LIBRARY})
+  set(Sndio_INCLUDE_DIRS ${Sndio_INCLUDE_DIR})
+endif()
+
+if(Sndio_FOUND AND NOT TARGET Sndio::Sndio)
+  add_library(Sndio::Sndio UNKNOWN IMPORTED)
+  set_target_properties(Sndio::Sndio PROPERTIES
+    IMPORTED_LOCATION "${Sndio_LIBRARY}"
+    INTERFACE_INCLUDE_DIRECTORIES "${Sndio_INCLUDE_DIR}"
+  )
+endif()
+
+mark_as_advanced(
+  Sndio_INCLUDE_DIR
+  Sndio_LIBRARY
+)