harfbuzz: don't compile support for unused APIs

Example code size reduction for release builds:
- `android-arm64`: -78.7 KB
- `emu-x86_64`: -149.5 KB
- `kindlepw2`: -94.2 KB

thirdparty/harfbuzz/CMakeLists.txt

@@ -26,14 +26,31 @@ list(APPEND CFG_CMD COMMAND
     ${SOURCE_DIR}
 )
 
+list(APPEND DEFINES
+    HB_DISABLE_DEPRECATED
+    HB_NO_BUFFER_MESSAGE
+    HB_NO_BUFFER_SERIALIZE
+    HB_NO_COLOR
+    HB_NO_LAYOUT_COLLECT_GLYPHS
+    HB_NO_LAYOUT_RARELY_USED
+    HB_NO_LAYOUT_UNUSED
+    HB_NO_META
+    HB_NO_PAINT
+    HB_NO_STYLE
+)
+
 # We've apparently hit a weird corner-case w/ XText where GCC/STL atomics *sometimes* horribly blow up on an ARM1136JF-S CPU w/ GCC 7.5 & up...
 # c.f., https://github.com/koreader/koreader/issues/5780 & https://github.com/koreader/koreader/issues/6024
 # NOTE: Our initial approach was to only disable atomics in a very dirty manner, which only helped with the first issue.
 #       This, on the other hand, appears to help with both.
 if(LEGACY OR POCKETBOOK)
-    list(APPEND CFG_CMD COMMAND ${ISED} "$a#define HB_NO_MT" config.h)
+    list(APPEND DEFINES HB_NO_MT)
 endif()
 
+list(TRANSFORM DEFINES REPLACE "(.+)" "-e;$a#define \\1")
+
+list(APPEND CFG_CMD COMMAND ${ISED} "$a/* KOReader Tweaks */" ${DEFINES} config.h)
+
 list(APPEND BUILD_CMD COMMAND ninja)
 
 list(APPEND INSTALL_CMD COMMAND ${MESON_INSTALL})