[matthiaskoenig]

Adds two things that currently have to be rebuilt by hand by anyone who wants roadrunner from
source: a build script that follows the CI workflow, and the smallest complete example of linking
against the result.

scripts/build_roadrunner.sh

Runs in an empty folder and produces a usable install tree, following
.github/workflows/main.yml: clone or update the checkout, download the prebuilt
libroadrunner-deps and llvm-build release assets for the host, configure with Ninja and ccache when
present, build the install target. Python bindings are on by default, Julia and Java off; SWIG
comes from PyPI because the stable ABI needs 4.4.1 or newer and the distribution packages are older.
--help lists the options (build type, jobs, tests, plugins, prefixes, --cmake-arg, ...).

The dependency and LLVM versions are read from the workflow matrix of the checkout being built
(libroadrunner_deps_release_version, llvm_name, llvm_release_version), so the script tracks
what CI uses rather than carrying its own copy.

Two things the workflow leaves implicit are handled explicitly:

• Asset resolution per host. The pinned dependency release no longer carries an ubuntu-24
  asset now that ubuntu-latest has moved on, so a literal transcription of the workflow 404s on
  Ubuntu 24.04. The script tries the host OS asset in the pinned release, then the manylinux_2_28
  asset from the same release, then the newest release that still has the host asset, and otherwise
  explains what to do.
• An RTTI check on the LLVM tree. cmake/FindLLVM.cmake strips -fno-rtti from the flags
  llvm-config reports and roadrunner compiles its back end with RTTI, so an LLVM built with
  LLVM_ENABLE_RTTI=OFF fails at link time with undefined typeinfo symbols. The script asks
  llvm-config --has-rtti first and stops with that explanation instead.

scripts/link-example

A separate cmake project, not built in tree, that imports the install tree through
ImportRoadrunnerAndDependencies.cmake, links roadrunner-static::roadrunner-static and simulates
dx/dt = -k*x from an inline SBML string, printing the trajectory and checking it against
exp(-t). It needs no data files and returns non-zero when the result is wrong, so it also serves
as a check that the installed cmake package files and headers are usable from outside the build.
build_roadrunner.sh --link-example builds and runs it after installing.

Verification

On Ubuntu 24.04 x86_64, from an empty folder: fresh clone, dependency and LLVM downloads, full
build, install, then both test suites and the example.

Done: roadrunner 2.11.1 (Release)
100% tests passed, 0 tests failed out of 3505     (C++)
100% tests passed, 0 tests failed out of 15       (Python)
x(1) = 0.367879, exp(-1) = 0.367879               (link example)

The example binary needs only libm, libstdc++, libgcc_s and libc. The --source-dir,
--deps-prefix, --llvm-prefix, --no-python, --run-tests and --link-example paths were
exercised, as were the RTTI check in both directions, with a stub llvm-config reporting NO.

Note on #1432

scripts/link-example needs the fix in #1432 to configure on Linux: without it the include of
ImportRoadrunnerAndDependencies.cmake stops at find_package(zlib ...), and with only that line
fixed it stops at sbml-static. The two are best merged together. #1432 also adds a documentation
section that points at scripts/link-example; if that one is merged without this one, the pointer
should be dropped.

[matthiaskoenig]

@luciansmith We have a ton of issues building and linking roadrunner based on the documentation. Adding a proper build script and example linking so this gets easier for people (and myself).