Embed git hash using vergen instead of mach (#30030)

Embed the git hash into the servo binary using vergen instead of using
custom Python code in mach. The benefit here is ones less difference
between a normal cargo run and building via mach in addition to removing
a bunch of code.

ports/libsimpleservo/api/Cargo.toml

@@ -31,6 +31,7 @@ libloading = "0.5"
 [build-dependencies]
 gl_generator = "0.14"
 serde_json = { workspace = true }
+vergen = { version = "8.0.0", features = [ "git", "gitcl" ]}
 
 [features]
 debugmozjs = ["libservo/debugmozjs"]

ports/libsimpleservo/api/build.rs

@@ -7,11 +7,24 @@ use serde_json::{self, Value};
 use std::env;
 use std::fs::File;
 use std::path::PathBuf;
+use vergen::EmitBuilder;
 
 fn main() {
     let target = env::var("TARGET").unwrap();
     let dest = PathBuf::from(&env::var("OUT_DIR").unwrap());
 
+    if let Err(error) = EmitBuilder::builder()
+        .fail_on_error()
+        .git_sha(true /* short */)
+        .emit()
+    {
+        println!(
+            "cargo:warning=Could not generate git version information: {:?}",
+            error
+        );
+        println!("cargo:rustc-env=VERGEN_GIT_SHA=nogit");
+    }
+
     // Generate GL bindings
     // For now, we only support EGL, and only on Windows and Android.
     if target.contains("android") || target.contains("windows") {

ports/libsimpleservo/api/src/lib.rs

@@ -185,12 +185,11 @@ pub struct ServoGlue {
 }
 
 pub fn servo_version() -> String {
-    let cargo_version = env!("CARGO_PKG_VERSION");
-    let git_info = option_env!("GIT_INFO");
-    match git_info {
-        Some(info) => format!("Servo {}{}", cargo_version, info),
-        None => format!("Servo {}", cargo_version),
-    }
+    format!(
+        "Servo {}-{}",
+        env!("CARGO_PKG_VERSION"),
+        env!("VERGEN_GIT_SHA")
+    )
 }
 
 /// Test if a url is valid.