No -pgmcxx option to correspond with -optcxx
GHC 8.10 now stores C++ compiler flags in its settings and supports
-optcxx to pass other flags, however the configure script doesn't detect or let users specify which C++ compiler to use, and there is also no corresponding
-pgmcxx option to override the C++ compiler used.
Lacking this configure option and flag makes it more complicated to implement better C++ support in Cabal/cabal-install.