dont hardcode build mode into BuildInfo (#11386)

`BuildInfo` used to hardcode the builld mode (i.e. debug vs. release) to
`cfg(debug_assertions)`, which ofc doesn't work when the `BuildInfo` is
coming from the wire (e.g. the `RerunCloud.version` gRPC endpoint).

Before:
```sh
$ pixi run redap version
client: redap_cli 0.3.0-alpha.1 (default tracy) [rustc 1.88.0 (6b00bc388 2025-06-23), LLVM 20.1.5] x86_64-unknown-linux-gnu (debug)
server: redap_frontend 0.3.0-alpha.1 [rustc 1.88.0 (6b00bc388 2025-06-23), LLVM 20.1.5] x86_64-unknown-linux-gnu (debug)  # <-- this server is actually a release build
```

After:
```sh
$ pixi run redap version
client: redap_cli 0.3.0-alpha.1 (default tracy) [rustc 1.88.0 (6b00bc388 2025-06-23), LLVM 20.1.5] x86_64-unknown-linux-gnu (debug)
server: redap_frontend 0.3.0-alpha.1 [rustc 1.88.0 (6b00bc388 2025-06-23), LLVM 20.1.5] x86_64-unknown-linux-gnu
```

Author: teh-cmc

crates/build/re_build_info/src/build_info.rs

@@ -50,6 +50,9 @@ pub struct BuildInfo {
     ///
     /// Empty if unknown.
     pub datetime: Cow<'static, str>,
+
+    /// True if this is a debug build.
+    pub is_debug_build: bool,
 }
 
 impl BuildInfo {
@@ -88,6 +91,7 @@ impl std::fmt::Display for BuildInfo {
             is_in_rerun_workspace: _,
             target_triple,
             datetime,
+            is_debug_build,
         } = self;
 
         let rustc_version = (!rustc_version.is_empty()).then(|| format!("rustc {rustc_version}"));
@@ -123,7 +127,7 @@ impl std::fmt::Display for BuildInfo {
             write!(f, ", built {datetime}")?;
         }
 
-        if cfg!(debug_assertions) {
+        if *is_debug_build {
             write!(f, " (debug)")?;
         }
 
@@ -177,6 +181,7 @@ fn crate_version_from_build_info_string() {
         is_in_rerun_workspace: true,
         target_triple: "x86_64-unknown-linux-gnu".into(),
         datetime: "".into(),
+        is_debug_build: true,
     };
 
     let build_info_str = build_info.to_string();

crates/build/re_build_info/src/lib.rs

@@ -26,6 +26,7 @@ macro_rules! build_info {
             is_in_rerun_workspace: env!("RE_BUILD_IS_IN_RERUN_WORKSPACE") == "yes",
             target_triple: env!("RE_BUILD_TARGET_TRIPLE").into(),
             datetime: env!("RE_BUILD_DATETIME").into(),
+            is_debug_build: cfg!(debug_assertions),
         }
     };
 }

crates/store/re_protos/proto/rerun/v1alpha1/common.proto

@@ -256,6 +256,9 @@ message BuildInfo {
   //
   // Empty if unknown.
   optional string build_time = 9;
+
+  /// True if this is a debug build.
+  optional bool is_debug_build = 10;
 }
 
 // Mirrors `re_build_info::CrateVersion`.

crates/store/re_protos/src/v1alpha1/rerun.common.v1alpha1.ext.rs

@@ -678,6 +678,7 @@ impl From<re_build_info::BuildInfo> for crate::common::v1alpha1::BuildInfo {
             git_branch: Some(build_info.git_branch.to_string()),
             target_triple: Some(build_info.target_triple.to_string()),
             build_time: Some(build_info.datetime.to_string()),
+            is_debug_build: Some(build_info.is_debug_build),
         }
     }
 }
@@ -695,6 +696,7 @@ impl From<crate::common::v1alpha1::BuildInfo> for re_build_info::BuildInfo {
             is_in_rerun_workspace: false,
             target_triple: build_info.target_triple().to_owned().into(),
             datetime: build_info.build_time().to_owned().into(),
+            is_debug_build: build_info.is_debug_build(),
         }
     }
 }

crates/store/re_protos/src/v1alpha1/rerun.common.v1alpha1.rs

@@ -428,6 +428,7 @@ impl Properties for re_build_info::BuildInfo {
             is_in_rerun_workspace,
             target_triple,
             datetime,
+            is_debug_build,
         } = self;
 
         event.insert("features", features.to_string());
@@ -437,7 +438,7 @@ impl Properties for re_build_info::BuildInfo {
         event.insert("llvm_version", llvm_version.to_string());
         event.insert("target", target_triple.to_string());
         event.insert("build_date", datetime.to_string());
-        event.insert("debug", cfg!(debug_assertions)); // debug-build?
+        event.insert("debug", is_debug_build);
         event.insert("rerun_workspace", is_in_rerun_workspace);
     }
 }

crates/utils/re_analytics/src/lib.rs

@@ -166,6 +166,7 @@ impl App {
             is_in_rerun_workspace: _,
             target_triple,
             datetime,
+            is_debug_build,
         } = self.build_info();
 
         ui.style_mut().wrap_mode = Some(egui::TextWrapMode::Extend);
@@ -177,8 +178,10 @@ impl App {
             format!("({short_git_hash})")
         };
 
+        let debug_label = if *is_debug_build { " (debug)" } else { "" };
+
         let mut label = format!(
-            "{crate_name} {version} {git_hash_suffix}\n\
+            "{crate_name} {version} {git_hash_suffix}{debug_label}\n\
             {target_triple}"
         );
 

crates/viewer/re_viewer/src/ui/rerun_menu.rs

@@ -172,7 +172,7 @@ fn show_warnings(frame: &eframe::Frame, ui: &mut egui::Ui, app_env: &crate::AppE
                 .small()
                 .color(ui.visuals().warn_fg_color),
         )
-        .on_hover_text("egui was compiled with debug assertions enabled.");
+        .on_hover_text("Rerun was compiled with debug assertions enabled.");
     }
 
     if !app_env.is_test() {