compiler-rt: simplify aligned memcpy loop

This change removes a few instruction from the aligned hot loop by not
updating the remaining size.

lib/compiler_rt/memcpy.zig

@@ -77,18 +77,13 @@ inline fn memcpy_aligned(
 ) void {
     @setRuntimeSafety(false);
 
-    var d = dest;
-    var s = src;
-    var n = len;
+    var i: usize = 0;
 
-    while (n >= size) {
-        d[0] = s[0];
-        n -= size;
-        d += 1;
-        s += 1;
+    while (i < len / size) : (i += 1) {
+        dest[i] = src[i];
     }
 
-    memcpy_remainder(size, @ptrCast(d), @ptrCast(s), n);
+    memcpy_remainder(size, @ptrCast(dest + i), @ptrCast(src + i), len % size);
 }
 
 inline fn memcpy_remainder(