Update OpenAL-soft to 1.21.1

libs/openal-soft/cmake/FindSndFile.cmake

@@ -0,0 +1,25 @@
+# - Try to find SndFile
+# Once done this will define
+#
+#  SNDFILE_FOUND - system has SndFile
+#  SndFile::SndFile - the SndFile target
+#
+
+find_path(SNDFILE_INCLUDE_DIR NAMES sndfile.h)
+
+find_library(SNDFILE_LIBRARY NAMES sndfile sndfile-1)
+
+# handle the QUIETLY and REQUIRED arguments and set SNDFILE_FOUND to TRUE if
+# all listed variables are TRUE
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(SndFile DEFAULT_MSG SNDFILE_LIBRARY SNDFILE_INCLUDE_DIR)
+
+if(SNDFILE_FOUND)
+    add_library(SndFile::SndFile UNKNOWN IMPORTED)
+    set_target_properties(SndFile::SndFile PROPERTIES
+        IMPORTED_LOCATION ${SNDFILE_LIBRARY}
+        INTERFACE_INCLUDE_DIRECTORIES ${SNDFILE_INCLUDE_DIR})
+endif()
+
+# show the SNDFILE_INCLUDE_DIR and SNDFILE_LIBRARY variables only in the advanced view
+mark_as_advanced(SNDFILE_INCLUDE_DIR SNDFILE_LIBRARY)