cli version: Put + before build data instead of -

Replace `jj 0.10.0-20231027-bb8af5adc4f98ff2` with `jj 0.10.0+20231027-bb8af5adc4f98ff2`.

According to https://semver.org, the build metadata should be separated by a
`+`, not `-`. If semver rules are pedantically followed, `jj
0.10.0-20231027-bb8af5adc4f98ff2` sorts before `jj 0.10.0`, whereas the build
metadata is ignored for the purposes of ordering.

I'm not sure whether anybody else is likely to treat the full `jj version`
string as a semver this pendantically, but we can :).

I discovered this when thinking about #2258; see that PR for a few more details
about pedantic semvers.

cli/build.rs

@@ -47,7 +47,7 @@ fn main() -> std::io::Result<()> {
     if let Some((mut git_hash, maybe_date)) = get_git_timestamp_and_hash() {
         git_hash.truncate(16);
         println!(
-            "cargo:rustc-env=JJ_VERSION={}-{}-{}",
+            "cargo:rustc-env=JJ_VERSION={}+{}-{}",
             version,
             maybe_date
                 .map(|d| d.format("%Y%m%d").to_string())

cli/tests/test_global_opts.rs

@@ -72,10 +72,10 @@ fn test_no_subcommand() {
     assert_matches!(
         sanitized.as_str(),
         "jj ?.??.?\n"
-            | "jj ?.??.?-????????-????????????????\n"
+            | "jj ?.??.?+????????-????????????????\n"
             // `dateunknown` turns into `??t?unknown` since d,a,e are hex digits.
             // TODO(ilyagr): This might be clearer as a regex.
-            | "jj ?.??.?-??t?unknown-????????????????\n"
+            | "jj ?.??.?+??t?unknown-????????????????\n"
     );
 
     let stdout = test_env.jj_cmd_success(test_env.env_root(), &["-R", "repo"]);