Remove unnecessary rebuild paths

Cargo tracks normal Rust dependencies and automatically figures out if changes
to Rust source files, `Cargo.{toml,lock}`, and `build.rs` necessitate a rebuild,
and if so of what. In some cases these checks are smarter than just comparing
file modification times, so not specifying such paths explicitly can reduce the
amount of rebuilding which happens, without skipping necessary rebuilding.

ja: this reverts b2aaf1db52 (Rebuild if src changed, 2025-03-28) and
460b93a (Rebuild on changes relevant to build artifacts, 2025-03-30)
which tried to fix #11332 ("moving Git HEAD does not invalidate cargo
build results").  But that expectation is overbearing.  It's better
to only rebuild if something else of relevance to the build output
has changed.

Closes #11736

build.rs

@@ -63,20 +63,11 @@ fn main() {
         let _ = std::fs::create_dir_all(sec1dir.to_str().unwrap());
     }
 
-    rsconf::rebuild_if_paths_changed(&[
-        "build.rs",
-        "Cargo.lock",
-        "Cargo.toml",
-        "crates/gettext-extraction",
-        "crates/printf",
-        "src",
-    ]);
-
     // These are necessary if built with embedded functions,
     // but only in release builds (because rust-embed in debug builds reads from the filesystem).
     #[cfg(feature = "embed-data")]
     #[cfg(not(debug_assertions))]
-    rsconf::rebuild_if_paths_changed(&["share"]);
+    rsconf::rebuild_if_path_changed("share");
 
     #[cfg(feature = "embed-data")]
     #[cfg(not(clippy))]
@@ -85,6 +76,7 @@ fn main() {
     #[cfg(feature = "gettext-extract")]
     rsconf::rebuild_if_env_changed("FISH_GETTEXT_EXTRACTION_FILE");
 
+    rsconf::rebuild_if_path_changed("src/libc.c");
     cc::Build::new().file("src/libc.c").compile("flibc.a");
 
     let mut build = cc::Build::new();