[temp] Manually find Ogg/Vorbis when using system libs

Revert once resolved:

ValveSoftware/steam-runtime#735

source/extern/CMakeLists.txt

@@ -37,7 +37,23 @@ endif()
 
 
 if(USE_SYSTEM_OGG)
-  find_package(Ogg REQUIRED GLOBAL)
+  if(OGG_INCLUDE_DIR)
+    # Already in cache, be silent
+    set(OGG_FIND_QUIETLY TRUE)
+  endif(OGG_INCLUDE_DIR)
+  find_path(OGG_INCLUDE_DIR ogg/ogg.h PATH_SUFFIXES include)
+  # MSVC built ogg may be named ogg_static.
+  # The provided project files name the library with the lib prefix.
+  find_library(OGG_LIBRARY NAMES ogg ogg_static libogg libogg_static)
+  # Handle the QUIETLY and REQUIRED arguments and set OGG_FOUND
+  # to TRUE if all listed variables are TRUE.
+  include(FindPackageHandleStandardArgs)
+  find_package_handle_standard_args(Ogg DEFAULT_MSG OGG_INCLUDE_DIR OGG_LIBRARY)
+
+  set(OGG_LIBRARIES ${OGG_LIBRARY})
+
+  mark_as_advanced(OGG_INCLUDE_DIR)
+  mark_as_advanced(OGG_LIBRARY)
 else()
   add_subdirectory(ogg)
   set_target_properties(ogg PROPERTIES FOLDER extern)
@@ -53,15 +69,46 @@ endif()
 
 
 if(USE_SYSTEM_VORBIS)
-  find_package(Vorbis REQUIRED GLOBAL)
+  if(VORBIS_INCLUDE_DIR)
+    # Already in cache, be silent
+    set(VORBIS_FIND_QUIETLY TRUE)
+  endif(VORBIS_INCLUDE_DIR)
+
+  find_package(Ogg)
+  if(OGG_FOUND)
+    find_path(VORBIS_INCLUDE_DIR vorbis/vorbisfile.h PATH_SUFFIXES include)
+    # MSVC built vorbis may be named vorbis_static
+    # The provided project files name the library with the lib prefix.
+    find_library(VORBIS_LIBRARY NAMES vorbis vorbis_static libvorbis libvorbis_static)
+    if (NOT ${VORBIS_LIBRARY} MATCHES ".framework")
+      find_library(VORBISFILE_LIBRARY NAMES vorbisfile vorbisfile_static libvorbisfile libvorbisfile_static)
+    else()
+      set(VORBISFILE_LIBRARY ${VORBIS_LIBRARY})
+    endif()
+    # Handle the QUIETLY and REQUIRED arguments and set VORBIS_FOUND
+    # to TRUE if all listed variables are TRUE.
+    include(FindPackageHandleStandardArgs)
+    find_package_handle_standard_args(Vorbis DEFAULT_MSG
+      VORBIS_INCLUDE_DIR
+      VORBIS_LIBRARY VORBISFILE_LIBRARY)
+  endif(OGG_FOUND)
+
+  if(VORBIS_FOUND)
+    set(VORBIS_LIBRARIES ${VORBISFILE_LIBRARY} ${VORBIS_LIBRARY}
+      ${OGG_LIBRARY})
+  else(VORBIS_FOUND)
+    set(VORBIS_LIBRARIES)
+  endif(VORBIS_FOUND)
+
+  mark_as_advanced(VORBIS_INCLUDE_DIR)
+  mark_as_advanced(VORBIS_LIBRARY VORBISFILE_LIBRARY)
 else()
   if(NOT USE_SYSTEM_OGG)
     set(OGG_LIBRARY ogg)
     set(OGG_INCLUDE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/ogg/include)
   endif()
   add_subdirectory(vorbis)
 endif()
-
 
 if (USE_SYSTEM_OPENAL)
   find_package(OpenAL REQUIRED GLOBAL)