Revert "Temporarily disable mumps within ngsolve, since recent upstre…

…am changes on MPI wrappers have broken mumps integration within ngsolve"

netgen now builds with USE_MPI_WRAPPER OFF by default, which restores MUMPS compatibility

This reverts commit 48c2636.

ngsolve/build.sh

@@ -60,7 +60,7 @@ cmake \
     -DCMAKE_CXX_COMPILER=$(which mpicxx) \
     -DCMAKE_SKIP_RPATH:BOOL=ON \
     -DCMAKE_INSTALL_PREFIX:PATH=$INSTALL_PREFIX \
-    -DUSE_MUMPS:BOOL=OFF \
+    -DUSE_MUMPS:BOOL=ON \
     -DUSE_UMFPACK:BOOL=ON \
     -DUSE_SUPERBUILD:BOOL=OFF \
     -DUSE_NATIVE_ARCH:BOOL=OFF \