cmake: Move OpenSLES detection to AudioCommon through find_package()

CMakeTests/FindOpenSLES.cmake

@@ -0,0 +1,28 @@
+# - Try to find OpenSLES
+# Once done this will define
+#  OPENSLES_FOUND - System has OpenSLES
+#  OPENSLES_INCLUDE_DIR - The OpenSLES include directory
+#  OPENSLES_LIBRARY - The library needed to use OpenSLES
+# An imported target OpenSLES::OpenSLES is also created, prefer this
+
+find_path(OPENSLES_INCLUDE_DIR
+  NAMES SLES/OpenSLES.h
+)
+
+find_library(OPENSLES_LIBRARY
+  NAMES OpenSLES
+)
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(OpenSLES  DEFAULT_MSG
+                                  OPENSLES_LIBRARY OPENSLES_INCLUDE_DIR)
+
+if(OpenSLES_FOUND)
+  add_library(OpenSLES::OpenSLES UNKNOWN IMPORTED)
+  set_target_properties(OpenSLES::OpenSLES PROPERTIES
+    IMPORTED_LOCATION ${OPENSLES_LIBRARY}
+    INTERFACE_INCLUDE_DIRECTORIES ${OPENSLES_INCLUDE_DIR}
+  )
+endif()
+
+mark_as_advanced(OPENSLES_INCLUDE_DIR OPENSLES_LIBRARY )