Avoids building grids on land points

- We had two coordinate modes that were building grids everywhere including
  on land points. This worked but is unnecessary.
- Avoids computations.
- No answer changes.

src/ALE/MOM_regridding.F90

@@ -1204,6 +1204,11 @@ subroutine build_sigma_grid( CS, G, GV, h, dzInterface )
   do i = G%isc-1,G%iec+1
     do j = G%jsc-1,G%jec+1
 
+      if (G%mask2dT(i,j)==0.) then
+        dzInterface(i,j,:) = 0.
+        cycle
+      endif
+
       ! The rest of the model defines grids integrating up from the bottom
       nominalDepth = G%bathyT(i,j)*GV%m_to_H
 
@@ -1293,6 +1298,12 @@ subroutine build_rho_grid( G, GV, h, tv, dzInterface, remapCS, CS )
   do j = G%jsc-1,G%jec+1
     do i = G%isc-1,G%iec+1
 
+      if (G%mask2dT(i,j)==0.) then
+        dzInterface(i,j,:) = 0.
+        cycle
+      endif
+
+
       ! Local depth (G%bathyT is positive)
       nominalDepth = G%bathyT(i,j)*GV%m_to_H