fix: Normalize CMake paths from 'dir/..' to '../dir' for compatibility

CMake and some build tools prefer the canonical '../dir/file' form over
'dir/../file', even though both are technically valid relative paths.

The pathdiff crate can generate 'dir/..' patterns when calculating
relative paths. This commit normalizes such patterns to the cleaner
'../dir' form for better tool compatibility.

Example:
- Before: cpp/../generated/file.cpp
- After: ../cpp/generated/file.cpp

Discovered while testing the RustBuffer fix on Android builds.

Author: sfourdrinier

crates/ubrn_cli/src/codegen/mod.rs

@@ -26,7 +26,26 @@ pub(crate) trait RenderedFile: DynTemplate {
         let from = file
             .parent()
             .expect("Expected this file to have a directory");
-        pathdiff::diff_utf8_paths(to, from).expect("Should be able to find a relative path")
+        let path = pathdiff::diff_utf8_paths(to, from).expect("Should be able to find a relative path");
+
+        // Normalize paths like "dir/../file" to "../dir/file" for better CMake compatibility
+        // This pattern can occur when calculating relative paths and is technically correct
+        // but some tools (like CMake) prefer the cleaner "../dir/file" form
+        let path_str = path.as_str();
+        let components: Vec<&str> = path_str.split('/').collect();
+
+        // Check if we have pattern like ["dir", "..", rest...]
+        if components.len() >= 2 && components[1] == ".." && !components[0].starts_with('.') {
+            let dir = components[0];
+            let rest = components[2..].join("/");
+            if rest.is_empty() {
+                Utf8PathBuf::from(format!("../{}", dir))
+            } else {
+                Utf8PathBuf::from(format!("../{}/{}", dir, rest))
+            }
+        } else {
+            path
+        }
     }
     fn filter_by(&self) -> bool {
         true