remove left over build.rs from nu-command (#8280)

@fdncred pointed out to me that post creation of the nu-cmd-lang crate
we probably don't need an extra build.rs
file in nu-command any longer now that the version command (and
build.rs) is located in nu-cmd-lang...

I am removing the redundancy...

crates/nu-command/Cargo.toml

@@ -1,6 +1,5 @@
 [package]
 authors = ["The Nushell Project Developers"]
-build = "build.rs"
 description = "Nushell's built-in commands"
 edition = "2021"
 license = "MIT"
@@ -155,9 +154,6 @@ sqlite = ["rusqlite"]                      # TODO: given that rusqlite is includ
 trash-support = ["trash"]
 which-support = ["which"]
 
-[build-dependencies]
-shadow-rs = { version = "0.20.0", default-features = false }
-
 [dev-dependencies]
 nu-test-support = { path = "../nu-test-support", version = "0.76.1" }
 

crates/nu-command/build.rs

@@ -1,20 +0,0 @@
-use std::process::Command;
-
-fn main() -> shadow_rs::SdResult<()> {
-    // Look up the current Git commit ourselves instead of relying on shadow_rs,
-    // because shadow_rs does it in a really slow-to-compile way (it builds libgit2)
-    let hash = get_git_hash().unwrap_or_default();
-    println!("cargo:rustc-env=NU_COMMIT_HASH={hash}");
-
-    shadow_rs::new()
-}
-
-fn get_git_hash() -> Option<String> {
-    Command::new("git")
-        .args(["rev-parse", "HEAD"])
-        .output()
-        .ok()
-        .filter(|output| output.status.success())
-        .and_then(|output| String::from_utf8(output.stdout).ok())
-        .map(|hash| hash.trim().to_string())
-}