cmake: Move AO detection to AudioCommon

CMakeTests/FindAO.cmake

@@ -0,0 +1,42 @@
+# - Find AO library
+# This module defines
+#  AO_INCLUDE_DIR
+#  AO_LIBRARIES
+#  AO_FOUND
+#
+# vim: expandtab sw=4 ts=4 sts=4:
+
+include(FindPkgConfig)
+pkg_check_modules (AO_PKG QUIET ao)
+
+find_path(AO_INCLUDE_DIR NAMES ao/ao.h
+  PATHS
+  ${AO_PKG_INCLUDE_DIRS}
+  /usr/include/ao
+  /usr/include
+  /usr/local/include/ao
+  /usr/local/include
+)
+
+find_library(AO_LIBRARIES NAMES ao
+  PATHS
+  ${AO_PKG_LIBRARY_DIRS}
+  /usr/lib
+  /usr/local/lib
+)
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(AO
+                                  REQUIRED_VARS AO_LIBRARIES AO_INCLUDE_DIR)
+
+if(AO_FOUND)
+  if(NOT TARGET AO::AO)
+    add_library(AO::AO UNKNOWN IMPORTED)
+    set_target_properties(AO::AO PROPERTIES
+      IMPORTED_LOCATION ${AO_LIBRARIES}
+      INTERFACE_INCLUDE_DIRECTORIES ${AO_INCLUDE_DIR}
+    )
+  endif()
+endif()
+
+mark_as_advanced(AO_INCLUDE_DIR AO_LIBRARIES)