Do not erase the flash to reset the storage on Nordic (google#337)

Otherwise the UICR registers are also reset which, among others, resets
the PSELRESET registers that permits resetting the dev-board from the
reset button.

crates/runner-nordic/memory.x

@@ -21,6 +21,7 @@ __flash_origin = __header_origin + __header_length;
 __flash_length = 0x00070000 - __header_length;
 __sother = 0x00010000 + (1 - RUNNER_SIDE) * 0x00070000;
 __eother = __sother + 0x00070000;
+/* Keep those values in sync with --reset-storage in xtask */
 __sstore = 0x000f0000;
 __estore = 0x00100000;
 

crates/xtask/src/main.rs

@@ -180,9 +180,9 @@ struct RunnerOptions {
     #[clap(long)]
     bundle: bool,
 
-    /// Erases all the flash first.
+    /// Resets the persistent storage before running.
     #[clap(long)]
-    erase_flash: bool,
+    reset_storage: bool,
 
     /// Prints the command lines to use GDB.
     #[clap(long)]
@@ -551,7 +551,7 @@ impl RunnerOptions {
         fs::touch("target/wasefire/applet.wasm")?;
         if run && self.name == "host" {
             let path = "target/wasefire/storage.bin";
-            if self.erase_flash && fs::exists(path) {
+            if self.reset_storage && fs::exists(path) {
                 fs::remove_file(path)?;
             }
             replace_command(cargo);
@@ -635,9 +635,10 @@ impl RunnerOptions {
                 Permissions::default(),
             )?)
         });
-        if self.erase_flash {
-            println!("Erasing the flash of {}", session.get()?.target().name);
-            flashing::erase_all(session.get()?, None)?;
+        if self.reset_storage {
+            println!("Erasing the persistent storage.");
+            // Keep those values in sync with crates/runner-nordic/memory.x.
+            flashing::erase_sectors(session.get()?, None, 240, 16)?;
         }
         if self.name == "nordic" {
             let mut cargo = Command::new("cargo");