cmake: Add stb-vorbis

This is a lightweight single-file Ogg Vorbis decoder which will be used
for Ogg playback instead of libogg/libvorbis.

thirdparty/CMakeLists.txt

@@ -666,3 +666,4 @@ if(xmp-lite_ADDED)
 endif()
 
 add_subdirectory(tcbrindle_span)
+add_subdirectory(stb_vorbis)

thirdparty/stb_vorbis/CMakeLists.txt

+# Update from https://github.com/nothings/stb
+# This doesn't use CPM because stb_vorbis.c has a weird header setup
+add_library(stb_vorbis STATIC stb_vorbis.c include/stb_vorbis.h)
+target_include_directories(stb_vorbis PUBLIC "${CMAKE_CURRENT_SOURCE_DIR}/include")

thirdparty/stb_vorbis/include/stb_vorbis.h

+#define STB_VORBIS_HEADER_ONLY
+#include "../stb_vorbis.c"