Fix version detection in re_viewer/build.rs

[jprochazk]

Something caused the CI to build the examples_manifest.json pointing to app.rerun.io to the commit 00fa796 instead of the version tag 0.9.1. That logic lives in this function:

rerun/crates/re_viewer/build.rs

Lines 192 to 213 in 65dc20c

	fn get_base_url() -> Result<String> {
	let mut base_url = re_build_tools::get_and_track_env_var("EXAMPLES_MANIFEST_BASE_URL")
	.unwrap_or_else(|_e| "https://demo.rerun.io/version/nightly".into());
	if re_build_tools::is_on_ci() {
	let sh = Shell::new()?;
	let branch = git_branch_name(&sh)?;
	// If we are on `main`, leave the base url at `version/nightly`
	if branch != "main" {
	if let Some(version) = parse_release_version(&branch) {
	// In builds on `release-x.y.z` branches, use `version/{x.y.z}`.
	base_url = format!("https://demo.rerun.io/version/{version}");
	} else {
	// On any other branch, use `commit/{short_sha}`.
	let sha = git_short_hash(&sh)?;
	base_url = format!("https://demo.rerun.io/commit/{sha}");
	}
	}
	}
	Ok(base_url)
	}