Add pthreads to includes for C files

build.rs

@@ -58,6 +58,7 @@ fn main() {
         .flag("-nostdlib")
         .include(&format!("{}/include", crate_dir))
         .include(&format!("{}/target/include", crate_dir))
+        .include(&format!("{}/pthreads-emb", crate_dir))
         .flag("-fno-stack-protector")
         .flag("-Wno-expansion-to-defined")
         .files(