Duplicate vsnwprintf symbol on Windows

Leading to failure of T5836:

Stderr ( T5836 ):
GHC runtime linker: fatal error: I found a duplicate definition for symbol
   __mingw_vsnwprintf
whilst processing object file
   C:\GitLabRunner\builds\8fc0e283\0\ghc\ghc\inplace\mingw\x86_64-w64-mingw32\lib\libmingwex.a
The symbol was previously defined in
   (GHCi built-in symbols)
This could be caused by:
   * Loading two different object files which export the same symbol
   * Specifying the same object file twice on the GHCi command line
   * An incorrect `package.conf' entry, causing some object to be
     loaded twice.
ghc-stage2.exe: panic! (the 'impossible' happened)
  (GHC version 8.9.20190303 for x86_64-unknown-mingw32):
	loadArchive "C:\\GitLabRunner\\builds\\8fc0e283\\0\\ghc\\ghc\\inplace\\mingw\\x86_64-w64-mingw32\\lib\\libmingwex.a": failed

Please report this as a GHC bug:  https://www.haskell.org/ghc/reportabug
*** unexpected failure for T5836(ghci)