Add support for xbuild (#212)

Signed-off-by: John Nunley <dev@notgull.net>

tools/codegen/base/xbuild.json

@@ -0,0 +1,13 @@
+{
+  "repository": "https://github.com/rust-mobile/xbuild",
+  "tag_prefix": "v",
+  "rust_crate": "${package}",
+  "asset_name": "${package}-${os_name}-x64${exe}",
+  "bin": "${package}-${os_name}-x64${exe}",
+  "version_range": ">= 0.2.0",
+  "platform": {
+    "x86_64_linux_gnu": {},
+    "x86_64_macos": {},
+    "x86_64_windows": {}
+  }
+}

tools/codegen/src/main.rs

@@ -178,6 +178,12 @@ fn main() -> Result<()> {
                 continue;
             }
         }
+
+        // Specifically skip versions of xbuild with build metadata.
+        if base_info.rust_crate.as_deref() == Some("xbuild") && !semver_version.build.is_empty() {
+            continue;
+        }
+
         let mut download_info = BTreeMap::new();
         for (&platform, base_download_info) in &base_info.platform {
             let asset_names = base_download_info