* Stop transpose(A) \ lu(B)' from overwriting `A`

This fixes the following bug I just found:
```julia
julia> A = randn(5,5)
5×5 Array{Float64,2}:
  0.485776   1.29655    0.0790172   0.66021   -1.49472
  0.971676  -1.01382    0.630476    0.479027  -0.843428
 -0.264609   0.392383   0.646729    0.510696   0.34913
 -0.795944  -2.47709   -1.81052    -1.0947    -0.30381
 -0.938873   2.16395   -1.33484    -0.745461   1.43709

julia> transpose(A) / lu(randn(5,5))' # should not change A
5×5 Adjoint{Float64,Array{Float64,2}}:
  14.36      11.9797   -7.32563    1.87016   -16.2731
 -18.4415   -13.7036   10.6455    -2.47396    19.9999
   8.0401     8.31723  -5.16714    2.13261    -9.637
   4.19849    3.9865   -1.98478    0.714778   -4.62445
  -5.36059   -2.60991   0.917052   0.290281    4.62547

julia> A # but does!
5×5 Array{Float64,2}:
  14.36     -18.4415    8.0401    4.19849   -5.36059
  11.9797   -13.7036    8.31723   3.9865    -2.60991
  -7.32563   10.6455   -5.16714  -1.98478    0.917052
   1.87016   -2.47396   2.13261   0.714778   0.290281
 -16.2731    19.9999   -9.637    -4.62445    4.62547
```

Co-authored-by: Daniel Karrasch <daniel.karrasch@posteo.de>
(cherry picked from commit 94398d1183b34fe37e63111165a850c75df94f5e)