fix(build): #234 use @response file for teensy link on Windows (#235)

Teensy boards (notably teensy41 with ~500 .o files) blew past Windows'
~32 KB CreateProcessW limit at link time, surfacing as "os error 206:
The filename or extension is too long". Linux (~128 KB) and macOS
(~256 KB) absorbed the same cmdline so CI stayed green while Windows
developers were blocked.

Mirror the existing ArmLinker (STM32/RP2040/NRF52) and Esp32Linker
pattern: on Windows, when args.len() > 50, write the linker args to a
hash-named .rsp under output_dir/tmp/ via
fbuild_core::response_file::write_response_file and invoke
arm-none-eabi-gcc with @<rsp>. Linux/macOS keep the direct invocation.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: zackees

crates/fbuild-build/src/teensy/teensy_linker.rs

@@ -101,8 +101,23 @@ impl Linker for TeensyLinker {
             tracing::info!("link: {}", args.join(" "));
         }
 
-        let args_ref: Vec<&str> = args.iter().map(|s| s.as_str()).collect();
-        let result = run_command(&args_ref, None, None, None)?;
+        // On Windows, use a response file to avoid command-line length limits
+        // (teensy41 produces ~500 .o files; see issue #234).
+        let result = if cfg!(windows) && args.len() > 50 {
+            let temp_dir = output_dir.join("tmp");
+            std::fs::create_dir_all(&temp_dir)?;
+            let rsp_content: Vec<String> = args[1..].iter().map(|a| a.replace('\\', "/")).collect();
+            let rsp_path = fbuild_core::response_file::write_response_file(
+                &rsp_content,
+                &temp_dir,
+                "teensy_link",
+            )?;
+            let rsp_arg = format!("@{}", rsp_path.display());
+            run_command(&[args[0].as_str(), &rsp_arg], None, None, None)?
+        } else {
+            let args_ref: Vec<&str> = args.iter().map(|s| s.as_str()).collect();
+            run_command(&args_ref, None, None, None)?
+        };
 
         if !result.success() {
             return Err(fbuild_core::FbuildError::BuildFailed(format!(