feat: run transaction hooks at boundaries and add configurable LTO flags

- execute transaction pre hooks at transaction start and post hooks at transaction end
- add batched hook execution with ordered "(n/total)" logging
- refactor install flows to plan package actions first, then run hooks around commits
- add `build.flags.ltoflags` and `build.flags.use_lto` (default: true)
- export `LTOFLAGS` and append LTO flags to `CFLAGS`, `CXXFLAGS`, and `LDFLAGS`
  unless `use_lto = false`
- make autotools CFLAGS expansion use the final computed CFLAGS value
- update spec parsing/appends, interactive TOML output, docs, and contrib build config
- bump project version to 0.8.0 and update `zip` to 8.2.0

src/package/interactive.rs

@@ -880,6 +880,19 @@ pub fn spec_to_minimal_toml(spec: &PackageSpec) -> anyhow::Result<String> {
             ),
         );
     }
+    if !spec.build.flags.ltoflags.is_empty() {
+        flags_tbl.insert(
+            "ltoflags".into(),
+            Value::Array(
+                spec.build
+                    .flags
+                    .ltoflags
+                    .iter()
+                    .map(|s| Value::String(s.clone()))
+                    .collect(),
+            ),
+        );
+    }
     if !spec.build.flags.keep.is_empty() {
         flags_tbl.insert(
             "keep".into(),
@@ -893,6 +906,9 @@ pub fn spec_to_minimal_toml(spec: &PackageSpec) -> anyhow::Result<String> {
             ),
         );
     }
+    if spec.build.flags.use_lto != defaults.use_lto {
+        flags_tbl.insert("use_lto".into(), Value::Boolean(spec.build.flags.use_lto));
+    }
     if spec.build.flags.no_flags != defaults.no_flags {
         flags_tbl.insert("no_flags".into(), Value::Boolean(spec.build.flags.no_flags));
     }
@@ -1474,8 +1490,10 @@ mod tests {
         flags.config_settings = vec!["editable_mode=compat".into()];
         flags.rustflags = vec!["-Ctarget-cpu=native".into()];
         flags.cxxflags = vec!["-O2".into(), "-fno-rtti".into()];
+        flags.ltoflags = vec!["-flto=auto".into()];
         flags.target = "x86_64-unknown-linux-gnu".into();
         flags.keep = vec!["etc/locale.gen".into()];
+        flags.use_lto = false;
         flags.no_flags = true;
         flags.no_strip = true;
         flags.no_delete_static = true;
@@ -1532,9 +1550,11 @@ mod tests {
         assert!(toml.contains("config_setting = ["));
         assert!(toml.contains("rustflags = ["));
         assert!(toml.contains("cxxflags = ["));
+        assert!(toml.contains("ltoflags = ["));
         assert!(toml.contains("target = \"x86_64-unknown-linux-gnu\""));
         assert!(toml.contains("keep = ["));
         assert!(toml.contains("\"etc/locale.gen\""));
+        assert!(toml.contains("use_lto = false"));
         assert!(toml.contains("no_flags = true"));
         assert!(toml.contains("no_strip = true"));
         assert!(toml.contains("no_delete_static = true"));