RISCV64: Add GHCi support

As we got a RTS linker for this architecture now, we can enable GHCi for
it.

hadrian/bindist/config.mk.in

@@ -142,7 +142,7 @@ GhcWithSMP := @GhcWithSMP@
 # Whether to include GHCi in the compiler.  Depends on whether the RTS linker
 # has support for this OS/ARCH combination.
 OsSupportsGHCi=$(strip $(patsubst $(TargetOS_CPP), YES, $(findstring $(TargetOS_CPP), mingw32 linux solaris2 freebsd dragonfly netbsd openbsd darwin kfreebsdgnu)))
-ArchSupportsGHCi=$(strip $(patsubst $(TargetArch_CPP), YES, $(findstring $(TargetArch_CPP), i386 x86_64 powerpc powerpc64 powerpc64le sparc sparc64 arm aarch64)))
+ArchSupportsGHCi=$(strip $(patsubst $(TargetArch_CPP), YES, $(findstring $(TargetArch_CPP), i386 x86_64 powerpc powerpc64 powerpc64le sparc sparc64 arm aarch64 riscv64)))
 
 ifeq "$(OsSupportsGHCi)$(ArchSupportsGHCi)" "YESYES"
 GhcWithInterpreter=YES