Libzmq Android build fails with NDK r27

[benjdero]

Issue description

Android build fails with latest NDK version r27.

Environment

• libzmq version (commit hash if unreleased): Latest commit on master 90b4f41
• OS: Ubuntu 24.04

Minimal test code / Steps to reproduce the issue

1. Setup Android build environment
2. Set export NDK_VERSION="android-ndk-r27b"
3. Run libzmq/builds/android/ci_build.sh

What's the actual result? (include assertion message & call stack if applicable)

Linking fails due to this error:

ld.lld: error: non-exported symbol '__aeabi_uldivmod' in '/tmp/android-ndk-r27b/toolchains/llvm/prebuilt/linux-x86_64/lib/clang/18/lib/linux/libclang_rt.builtins-arm-android.a(aeabi_uldivmod.S.o)' is referenced by DSO 'src/.libs/libzmq.so'
ld.lld: error: non-exported symbol '__aeabi_uldivmod' in '/tmp/android-ndk-r27b/toolchains/llvm/prebuilt/linux-x86_64/lib/clang/18/lib/linux/libclang_rt.builtins-arm-android.a(aeabi_uldivmod.S.o)' is referenced by DSO 'src/.libs/libzmq.so'
ld.lld: error: non-exported symbol '__aeabi_idiv' in '/tmp/android-ndk-r27b/toolchains/llvm/prebuilt/linux-x86_64/lib/clang/18/lib/linux/libclang_rt.builtins-arm-android.a(divsi3.S.o)' is referenced by DSO 'src/.libs/libzmq.so'
[...]

What's the expected result?

It can be fixed by replacing -lc++_shared by -static-libstdc++ in the LDFLAGS there

I'm not sure if this is the right solution, as it is far beyond my C++ knowledge.

Android NDK r27 changelog mention dropping "unused libclang" (last line of changelog)

This open issue on NDK github page mention reintroducing libclang properly.

What should we do? @bluca @sappo

[rbebb]

Just wanted to leave a comment saying that it would be great to have support for NDK 27😄