harfbuzz recipe build fail

### Logs

```

make[4]: Entering directory '/home/bobf/ex/regression/.buildozer/android/platform/build-arm64-v8a/build/other_builds/harfbuzz/arm64-v8a__ndk_target_21/harfbuzz/src'
make[4]: warning: -j12 forced in submake: resetting jobserver mode.
GEN libharfbuzz.la
GEN harfbuzz.pc
GEN harfbuzz-subset.pc
CXX libharfbuzz_subset_la-hb-subset-cff1.lo
CXXLD main
CXXLD test
CXXLD test-buffer-serialize
CXXLD test-ot-meta
CXXLD test-ot-name
CXXLD test-gpos-size-params
CXXLD test-gsub-would-substitute
hb-subset-cff1.cc:472:33: error: variable 'supp_size' set but not used [-Werror,-Wunused-but-set-variable]
unsigned int size0, size1, supp_size;
^
1 error generated.
```

从 Android arm64-v8a 目标的 HarfBuzz recipe build 开始，并检查 hb-subset-cff1.cc:472 处的编译器诊断信息。重现记录中的构建失败，并确定 recipe 或构建配置需要更改什么；当 HarfBuzz recipe 构建时不会将此警告视为错误，即表示完成。

由索引模型根据 Issue 内容生成。