Make version dynamic (#2403)

`pyproject.toml` now reads `VERSION`.

Also, ignore CPM cache.

Closes: #2201

.gitignore

@@ -105,3 +105,4 @@ _skbuild
 
 # generated by test scripts
 results
+/_deps/

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "arbor"
-version = "0.10.0" # TODO: make dependent on VERSION file. Blocked by https://github.com/scikit-build/scikit-build-core/issues/230
+dynamic = ["version"]
 readme = {file = "README.md", content-type = "text/markdown"}
 license = {file = "LICENSE"}
 description = "High performance simulation of networks of multicompartment neurons."
@@ -39,6 +39,10 @@ sdist.include = ["ext/*/.git"]
 wheel.install-dir = "arbor"
 wheel.packages = []
 
+[tool.scikit-build.metadata.version]
+provider = "scikit_build_core.metadata.regex"
+input = "VERSION"
+regex = "(?P<value>\\d+\\.\\d+\\.\\d+(-.+)?)"
 
 [tool.ruff]
 exclude = [