LinearForms.F90: Avoid compiler error with GFortran 10 or newer.

The `dgemm` and `dgemv` functions expect rank-2 for some of their
arguments. Newer compilers (e.g., GFortran 10 or newer) emit an error
if the rank of the arguments don't match.
That error is currently downgraded to a warning by adding
`-fallow-argument-mismatch` to the Fortran compiler flags for GFortran.

Avoid that error/warning by passing the respective argument with the
expected rank.

fem/src/LinearForms.F90

@@ -130,7 +130,7 @@ SUBROUTINE LinearForms_GradUdotGradU(m, n, dim, GradU, weight, G, alpha)
           END IF
           ! Compute matrix \grad u \dot \grad u for dim=k
           CALL DGEMM('T', 'N', n, n, blklen, &
-                1D0, GradU(ii,1,k), ldbasis, &
+                1D0, [[GradU(ii,1,k)]], ldbasis, &
                 wrk, ldwrk, 1D0, G, ldk)
         END DO
       END IF
@@ -252,7 +252,7 @@ SUBROUTINE LinearForms_GradUdotU(m, n, dim, GradU, U, weight, G, alpha, beta)
           END IF
           ! Compute matrix \grad u \dot u for dim=k
           CALL DGEMM('T', 'N', n, n, blklen, &
-                1D0, U(ii,1), lbasis, &
+                1D0, [[U(ii,1)]], lbasis, &
                 wrk, ldwrk, 1D0, G, ldk)
         END DO
       END IF
@@ -326,7 +326,7 @@ SUBROUTINE LinearForms_UdotV(m, n, dim, U, V, weight, G, alpha)
           END IF
           ! Compute matrix u \dot u
           CALL DGEMM('T', 'N', n, n, blklen, &
-               1D0, U(ii,1), ldbasis, &
+               1D0, [[U(ii,1)]], ldbasis, &
                wrk, ldwrk, 1D0, G, ldk)
        END IF
     END DO ! Vector blocks
@@ -398,7 +398,7 @@ SUBROUTINE LinearForms_UdotU(m, n, dim, U, weight, G, alpha)
           END IF
           ! Compute matrix u \dot u
           CALL DGEMM('T', 'N', n, n, blklen, &
-               1D0, U(ii,1), ldbasis, &
+               1D0, [[U(ii,1)]], ldbasis, &
                wrk, ldwrk, 1D0, G, ldk)
        END IF
     END DO ! Vector blocks
@@ -477,7 +477,7 @@ SUBROUTINE LinearForms_UdotF(m, n, U, weight, F, UdotF, alpha)
         END IF
 
         CALL DGEMV('T', blklen, n, &
-              1D0, U(ii,1), SIZE(U,1), wrk, 1, 1D0, UdotF, 1)
+              1D0, [[U(ii,1)]], SIZE(U,1), wrk, 1, 1D0, UdotF, 1)
       END IF
     END DO
   END SUBROUTINE LinearForms_UdotF