Align x86_64 "universal" linux build with aarch64

[lloeki]

There's an asymmetry with x86_64:

• there's libddwaf-1.0.11-linux-x86_64-static.tar.gz which is a static lib that should work on alpine and debian but that I can't use for the Ruby bindings since I'm using FFI which needs a shared lib
• there's libddwaf-1.0.11-linux-x86_64-muslc.tar.gz and libddwaf-1.0.11-linux-x86_64-glibc.tar.gz which do have shared libs but don't run on both, and should be fine but are a bit awkward as to being different for another cpu arch but the difference is in fact unrelated to the cpu arch, just that it turns out it's using a different build process.

I have the feeling that libddwaf-1.0.11-linux-x86_64-static.tar.gz should drop the -static from the name and reuse/follow as much as possible the build process of libddwaf-1.0.11-linux-aarch64.tar.gz, resulting in a static+shared lib build for x86_64, uniform with aarch64. The build should be very similar expect without the ARM toolchain, so probably using the regular compiler instead of the cross compiling one should be fine, and then tests would run without qemu.

We could duplicate the aarch64 dir as x86_64 and proceed with the adjustments, to "make it work" and surface possible commonalities. A future step would look into sharing stuff to "make it right".