Disable usage of sys_siglist function to workaround issues on alpine

[normanmaurer]

Motivation:

When we try to use our static compiled version on alpine it fails due missing sys_siglist. We can workaround this by letting apr use its own implementation.

Modifications:

Use ac_cv_have_decl_sys_siglist=no when compiling APR.

Result:

netty-tcnative-boringssl-static should be useable on alpine. Fixes #853

[normanmaurer]

ok problem is still there... need to investigate further

[normanmaurer]

Wohoo... This worked:

/tmp/build-pr-centos7-aarch64-target-jars/boringssl-static/target # ldd META-INF/native/libnetty_tcnative_linux_aarch_64.so
	/lib/ld-musl-aarch64.so.1 (0xffffa7a25000)
	librt.so.1 => /lib/ld-musl-aarch64.so.1 (0xffffa7a25000)
	libcrypt.so.1 => /lib/libcrypt.so.1 (0xffffa77f5000)
	libdl.so.2 => /lib/ld-musl-aarch64.so.1 (0xffffa7a25000)
	libc.so.6 => /lib/ld-musl-aarch64.so.1 (0xffffa7a25000)
	libucontext.so.1 => /lib/libucontext.so.1 (0xffffa77d4000)
	libobstack.so.1 => /usr/lib/libobstack.so.1 (0xffffa77b3000)