Re-add WRITE_SIZE as it seems to be the same for all regions

stm32-metapac-gen/src/lib.rs

@@ -132,6 +132,18 @@ impl Gen {
         writeln!(&mut extra, "pub const FLASH_BASE: usize = {};", first_flash.address).unwrap();
         writeln!(&mut extra, "pub const FLASH_SIZE: usize = {};", total_flash_size).unwrap();
 
+        let write_sizes: HashSet<_> = flash_regions
+            .iter()
+            .map(|r| r.settings.as_ref().unwrap().write_size)
+            .collect();
+        assert_eq!(1, write_sizes.len());
+        writeln!(
+            &mut extra,
+            "pub const WRITE_SIZE: usize = {};",
+            write_sizes.iter().next().unwrap()
+        )
+        .unwrap();
+
         // Cleanups!
         transform::sort::Sort {}.run(&mut ir).unwrap();
         transform::Sanitize {}.run(&mut ir).unwrap();