Add proper cfg

Author: mu001999

library/core/src/ptr/alignment.rs

@@ -240,6 +240,7 @@ type AlignmentEnum = AlignmentEnum32;
 #[cfg(target_pointer_width = "64")]
 type AlignmentEnum = AlignmentEnum64;
 
+#[cfg(target_pointer_width = "16")]
 #[derive(Copy, Clone, PartialEq, Eq)]
 #[repr(u16)]
 enum AlignmentEnum16 {
@@ -261,6 +262,7 @@ enum AlignmentEnum16 {
     _Align1Shl15 = 1 << 15,
 }
 
+#[cfg(target_pointer_width = "32")]
 #[derive(Copy, Clone, PartialEq, Eq)]
 #[repr(u32)]
 enum AlignmentEnum32 {