build(xbuild): output Rust binding file even if no bindings were specified

diff --git a/core/embed/xbuild/src/clibrary/rust_bindings.rs b/core/embed/xbuild/src/clibrary/rust_bindings.rs
index ed992bd0..288d1b0c 100644
--- a/core/embed/xbuild/src/clibrary/rust_bindings.rs
+++ b/core/embed/xbuild/src/clibrary/rust_bindings.rs
@@ -21,7 +21,8 @@ impl CLibrary {
     /// Generates rust bininding (a .rs file) from the configured builder and
     /// writes it to the OUT_DIR.
     pub(crate) fn generate_rust_bindings(&mut self, use_cc_includes: bool) -> Result<()> {
-        if let Some(builder) = self.builder.take() {
+        let out_file = path_from_env("OUT_DIR")?.join(links_name()? + ".rs");
+        let content = if let Some(builder) = self.builder.take() {
             let mut attrs = self.get_merged_attrs();
 
             if use_cc_includes {
@@ -35,9 +36,7 @@ impl CLibrary {
             attrs.remove_flag("-mcmse");
             attrs.remove_flag("-fsingle-precision-constant");
 
-            let out_file = path_from_env("OUT_DIR")?.join(links_name()? + ".rs");
-            let tmp_out_file = out_file.with_extension("rs.tmp");
-
+            let mut content = Vec::<u8>::new();
             builder
                 .clang_args(attrs.to_compiler_args())
                 // Customize the standard types.
@@ -52,35 +51,34 @@ impl CLibrary {
                 .parse_callbacks(Box::new(bindgen::CargoCallbacks::new()))
                 .generate()
                 .context("Unable to generate bindings")?
-                .write_to_file(&tmp_out_file)
-                .context(format!(
-                    "Unable to write bindings to {}",
-                    tmp_out_file.display()
-                ))?;
+                .write(Box::new(&mut content))
+                .context("Unable to write bindings to a buffer")?;
+
+            content
+        } else {
+            // just empty file
+            Vec::<u8>::new()
+        };
 
-            // Bindgen writes the output file even if the content is unchanged,
-            // which causes unnecessary recompilations. To avoid this, we
-            // compare the generated file with the existing one and only replace
-            // it if there are changes.
-            replace_if_different(&tmp_out_file, &out_file)?;
-        }
+        // Bindgen writes the output file even if the content is unchanged,
+        // which causes unnecessary recompilations. To avoid this, we
+        // compare the generated file with the existing one and only replace
+        // it if there are changes.
+        maybe_replace(content, &out_file)?;
         Ok(())
     }
 }
 
-fn replace_if_different(src: &std::path::Path, dst: &std::path::Path) -> Result<()> {
-    if dst.exists() {
-        let src_content = std::fs::read(src).context("Failed to read temporary bindings file")?;
+fn maybe_replace(src_content: Vec<u8>, dst: &std::path::Path) -> Result<()> {
+    let should_write = if !dst.exists() {
+        true
+    } else {
         let dst_content = std::fs::read(dst).context("Failed to read existing bindings file")?;
+        src_content != dst_content
+    };
 
-        if src_content == dst_content {
-            // Files are identical, no need to replace
-            // Clean up the temporary file
-            std::fs::remove_file(src).context("Failed to remove temporary bindings file")?;
-            return Ok(());
-        }
+    if should_write {
+        std::fs::write(dst, src_content).context("Failed to write empty bindings file")?;
     }
-
-    std::fs::rename(src, dst).context("Failed to replace bindings file")?;
     Ok(())
 }