factor into workspace, improve features & deps

examples/lpc55s28-evk/build.rs

@@ -0,0 +1,5 @@
+// Find the actual path of memory.x and add it to link search, required for building in workspace
+fn main() {
+    let manifest_dir = std::env::var("CARGO_MANIFEST_DIR").unwrap();
+    println!("cargo:rustc-link-search={}", manifest_dir);
+}