Missing `libm` linkage causes undefined symbol errors

[BwL1289]

When building asyncpg the compiled extension modules fail to load at runtime with errors like:

undefined symbol: log10	(./lib/python3.12/site-packages/asyncpg/pgproto/pgproto.cpython-312-aarch64-linux-gnu.so)

This happens because the C extensions use math functions from libm but don't explicitly link against it.

[./lib/python3.12/site-packages/asyncpg/pgproto/pgproto.cpython-312-aarch64-linux-gnu.so]:
    linux-vdso.so.1 (0x0000ffff9e066000)
    libc.so.6 => /lib64/libc.so.6 (0x0000ffff9ddce000)
    /lib/ld-linux-aarch64.so.1 (0x0000ffff9e019000)
undefined symbol: log10	(./lib/python3.12/site-packages/asyncpg/pgproto/pgproto.cpython-312-aarch64-linux-gnu.so)

I'm building from an older commit, but this may be still an issue in newer versions.

Environment

• OS: Amazon Linux 2023 (aarch64)
• Python: 3.12.7
• Compiler: Clang 20git
• asyncpg commit: d0797f1

[BwL1289]

Solution is to explicitly link libm in setup.py:

...
setuptools.extension.Extension(
            "asyncpg.pgproto.pgproto",
            ["asyncpg/pgproto/pgproto.pyx"],
            extra_compile_args=CFLAGS,
            extra_link_args=LDFLAGS),
            libraries=["m"],
...