Bug#948109: z3: FTBFS on riscv64, needs -latomic, blocks rustc:riscv64

[Fabian Wolff]

I've mostly finished porting the package to the CMake build system now, so
to avoid further confusion as to which parts of which patches should be
applied, what I would suggest is for you to just have a look at the Salsa
repository and port your patches so that I know precisely what changes you
need (just open a MR or something):

  https://salsa.debian.org/pkg-llvm-team/z3/tree/cmake

I hope this won't be too much work for you, but the CMake build scripts are
actually a lot easier to work with, and the new debian/rules is also much
shorter, so it shouldn't be too much effort, I think! This would also give
you the opportunity to test whether my changes, together with your patch,
will actually work on riscv64.


Ximin: I do realize that coordinating the SONAME with upstream would be
preferable, but upstream's handling of it does not appear to be very mature
yet (e. g. the two build systems generate different SONAMEs, and the CMake
scripts set the SONAME to MAJOR_VERSION.MINOR_VERSION, which is incorrect
because the SONAME should count ABI compatibility breaks and not version
numbers). Perhaps I should discuss this with upstream at some point, but
for now, I don't want to cause any unnecessary transitions just because
the build system changed.