All our targets need obsd-nat.o and kvm etc -> dedup.
Add aarch64 and riscv64 support.

Index: gdb/configure.nat
--- gdb/configure.nat.orig
+++ gdb/configure.nat
@@ -48,7 +48,6 @@
 #
 # - nat_makefile_frag must contain the full path of the file.
 
-
 # This first case is useful for filling default values for each
 # gdb_host.
 case ${gdb_host} in
@@ -72,7 +71,8 @@ case ${gdb_host} in
 	HAVE_NATIVE_GCORE_HOST=1
 	;;
     obsd*)
-	NATDEPFILES='fork-child.o nat/fork-inferior.o inf-ptrace.o'
+	NATDEPFILES='fork-child.o nat/fork-inferior.o inf-ptrace.o bsd-kvm.o obsd-nat.o'
+	LOADLIBES='-lkvm'
 	;;
     cygwin*)
 	NATDEPFILES='x86-nat.o nat/x86-dregs.o windows-nat.o'
@@ -416,49 +416,54 @@ case ${gdb_host} in
 	case ${gdb_host_cpu} in
 	    i386)
 		# Host: OpenBSD/i386 ELF
-		NATDEPFILES="${NATDEPFILES} obsd-nat.o x86-bsd-nat.o \
-		i386-bsd-nat.o i386-obsd-nat.o bsd-kvm.o"
-		LOADLIBES='-lkvm'
+		NATDEPFILES="${NATDEPFILES} x86-bsd-nat.o \
+		i386-bsd-nat.o i386-obsd-nat.o"
 		;;
 	    m68k)
 		# Host: OpenBSD/m68k
-		NATDEPFILES="${NATDEPFILES} m68k-bsd-nat.o bsd-kvm.o"
-		LOADLIBES='-lkvm'
+		NATDEPFILES="${NATDEPFILES} m68k-bsd-nat.o"
 		;;
 	    pa)
 		# Host: OpenBSD/hppa
-		NATDEPFILES="${NATDEPFILES} obsd-nat.o hppa-obsd-nat.o"
+		NATDEPFILES="${NATDEPFILES} hppa-obsd-nat.o"
 		;;
 	    powerpc)
 		# Host: OpenBSD/powerpc
-		NATDEPFILES="${NATDEPFILES} obsd-nat.o ppc-obsd-nat.o bsd-kvm.o"
-		LOADLIBES='-lkvm'
+		NATDEPFILES="${NATDEPFILES} ppc-obsd-nat.o"
 		;;
 	    vax)
 		# Host: OpenBSD/vax
-		NATDEPFILES="${NATDEPFILES} vax-bsd-nat.o bsd-kvm.o"
-		LOADLIBES='-lkvm'
+		NATDEPFILES="${NATDEPFILES} vax-bsd-nat.o"
 		;;
 	esac
 	;;
     obsd64)
 	case ${gdb_host_cpu} in
+	    aarch64)
+		# Host: OpenBSD/arm64
+		NATDEPFILES="${NATDEPFILES} aarch64-obsd-nat.o"
+		;;
 	    i386)
 		# Host: OpenBSD/amd64
-		NATDEPFILES="${NATDEPFILES} obsd-nat.o amd64-nat.o x86-nat.o \
-		x86-bsd-nat.o amd64-bsd-nat.o amd64-obsd-nat.o bsd-kvm.o \
-		nat/x86-dregs.o"
-		LOADLIBES='-lkvm'
+		NATDEPFILES="${NATDEPFILES} amd64-nat.o \
+		x86-bsd-nat.o amd64-bsd-nat.o amd64-obsd-nat.o"
 		;;
 	    mips)
 		# Host: OpenBSD/mips64
-		NATDEPFILES="${NATDEPFILES} obsd-nat.o mips64-obsd-nat.o"
+		NATDEPFILES="${NATDEPFILES} mips64-obsd-nat.o"
 		;;
+	    powerpc)
+		# Host: OpenBSD/powerpc64
+		NATDEPFILES="${NATDEPFILES} ppc64-obsd-nat.o"
+		;;
+	    riscv64)
+		# Host: OpenBSD/riscv64
+		NATDEPFILES="${NATDEPFILES} riscv-obsd-nat.o"
+		;;
 	    sparc)
 		# Host: OpenBSD/sparc64
-		NATDEPFILES="${NATDEPFILES} obsd-nat.o sparc64-obsd-nat.o \
-		sparc-nat.o bsd-kvm.o"
-		LOADLIBES='-lkvm'
+		NATDEPFILES="${NATDEPFILES} sparc64-obsd-nat.o \
+		sparc-nat.o"
 		;;
 	esac
 	;;