Linking fails due to introduction of `-lunwind` on Android platform with 1.68

[TheBlueMatt]

Upgraded to 1.68.0 from 1.67.1 this morning and linking for an Android target seems to be failing due to the introduction of -lunwind passed to the linker.

Relevant CI snippets from the build run:

 + export 'CFLAGS_x86_64_linux_android=-ffile-prefix-map=/github/home/.cargo= -frandom-seed=42'
+ CFLAGS_x86_64_linux_android='-ffile-prefix-map=/github/home/.cargo= -frandom-seed=42'
+ export CC_x86_64_linux_android=x86_64-linux-android24-clang
+ CC_x86_64_linux_android=x86_64-linux-android24-clang
+ RUSTFLAGS='--cfg=c_bindings --remap-path-prefix /__w/ldk-garbagecollected/ldk-garbagecollected/rust-lightning=rust-lightning --remap-path-prefix /__w/ldk-garbagecollected/ldk-garbagecollected/ldk-c-bindings=ldk-c-bindings --remap-path-prefix /github/home/.cargo= -C embed-bitcode=yes -C lto -C linker=x86_64-linux-android24-clang'
+ CARGO_PROFILE_RELEASE_LTO=true
+ cargo build --features=std -v --release --target x86_64-linux-android

Note that Cargo.toml for the crate also includes:

[lib]
name = "ldk"
crate-type = ["staticlib", "cdylib"]

[features]
...
[dependencies]
...

[profile.dev]
panic = "abort"

[profile.release]
panic = "abort"

Ultimately it errors with:

error: linking with `x86_64-linux-android24-clang` failed: exit status: 1
  |
  = note: LC_ALL="C" PATH="/github/home/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/bin:/github/home/.cargo/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/__w/ldk-garbagecollected/ldk-garbagecollected/android-ndk-r22b/toolchains/llvm/prebuilt/linux-x86_64/bin:~/.cargo/bin" VSLANG="1033" "x86_64-linux-android24-clang" "-Wl,--version-script=/tmp/rustchxgOwt/list" "-m64" "/tmp/rustchxgOwt/symbols.o" "/__w/ldk-garbagecollected/ldk-garbagecollected/ldk-c-bindings/lightning-c-bindings/target/x86_64-linux-android/release/deps/ldk.ldk.e1ac8e4d-cgu.1.rcgu.o" "-Wl,--as-needed" "-L" "/__w/ldk-garbagecollected/ldk-garbagecollected/ldk-c-bindings/lightning-c-bindings/target/x86_64-linux-android/release/deps" "-L" "/__w/ldk-garbagecollected/ldk-garbagecollected/ldk-c-bindings/lightning-c-bindings/target/release/deps" "-L" "/__w/ldk-garbagecollected/ldk-garbagecollected/ldk-c-bindings/lightning-c-bindings/target/x86_64-linux-android/release/build/secp256k1-sys-f58fb0f1ec277fc7/out" "-L" "/github/home/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-linux-android/lib" "-Wl,-Bstatic" "/tmp/rustchxgOwt/libsecp256k1_sys-513b9661f2c3756c.rlib" "/github/home/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-linux-android/lib/libcompiler_builtins-367de5b14a245593.rlib" "-Wl,-Bdynamic" "-ldl" "-llog" "-lunwind" "-ldl" "-lm" "-lc" "-Wl,--eh-frame-hdr" "-Wl,-znoexecstack" "-L" "/github/home/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-linux-android/lib" "-o" "/__w/ldk-garbagecollected/ldk-garbagecollected/ldk-c-bindings/lightning-c-bindings/target/x86_64-linux-android/release/deps/libldk.so" "-Wl,--gc-sections" "-shared" "-Wl,-zrelro,-znow" "-Wl,-O1" "-nodefaultlibs"
  = note: ld: error: unable to find library -lunwind
          clang: error: linker command failed with exit code 1 (use -v to see invocation)

Exact replication can be found in the CI script at https://github.com/TheBlueMatt/ldk-garbagecollected/blob/11c3a5cc649678de124295c7aff725df00905a0d/.github/workflows/build.yml#L253

[cuviper]

You'll need a newer NDK: https://blog.rust-lang.org/2023/01/09/android-ndk-update-r25.html

[TheBlueMatt]

Ah, okay, will just pin to rust 1.67.