add skip-data-init feature to optionally skip .data copy at reset

Author: KushalMeghani1644

cortex-m-rt/CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Mark `pre_init` as deprecated
 - Add `set_msplim` feature to conditionally set the MSPLIM register at device
   reset ([#580]).
+- Add `skip-data-init` feature to optionally skip copying the `.data` section.
 
 ## [v0.7.5]
 

cortex-m-rt/src/lib.rs

@@ -513,6 +513,11 @@
 #![deny(missing_docs)]
 #![no_std]
 
+#[cfg(all(feature = "skip-data-init", feature = "zero-init-ram"))]
+compile_error!(
+    "features `skip-data-init` and `zero-init-ram` cannot be enabled at the same time"
+);
+
 extern crate cortex_m_rt_macros as macros;
 
 /// The 32-bit value the stack is painted with before the program runs.