package/gdb: fix build of gdb on riscv

Build of gdb on riscv without host-gdb is broken since commit
4ecd247ead22a6cfb87a4ffafc4be05201328aef because BR2_GDB_VERSION_10 is
never defined if BR2_PACKAGE_HOST_GDB is not selected resulting in the
following build failure:

/bin/bash: line 0: cd: /tmp/instance-0/output-1/build/gdb-10.1/gdb/gdbserver: No such file or directory

So add a BR2_PACKAGE_GDB_TOPLEVEL hidden option as suggested by Thomas
Petazzoni.

Fixes:
 - http://autobuild.buildroot.org/results/ce47d616ee79d5f735779570ebc3b4a9c0f64c6a

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/gdb/Config.in.host

@@ -93,3 +93,12 @@ config BR2_GDB_VERSION
 	default "9.2"      if BR2_GDB_VERSION_9_2 || (!BR2_PACKAGE_HOST_GDB && !BR2_riscv)
 	default "10.2"	   if BR2_GDB_VERSION_10 || (!BR2_PACKAGE_HOST_GDB && BR2_riscv)
 	depends on BR2_PACKAGE_GDB || BR2_PACKAGE_HOST_GDB
+
+# recent gdb versions (>= 10) have gdbserver moved at the top-level,
+# which requires a different build logic.
+config BR2_PACKAGE_GDB_TOPLEVEL
+	bool
+	default y if BR2_arc
+	default y if BR2_GDB_VERSION_10
+	default y if !BR2_PACKAGE_HOST_GDB && BR2_riscv
+	depends on BR2_PACKAGE_GDB || BR2_PACKAGE_HOST_GDB

package/gdb/gdb.mk

@@ -8,19 +8,10 @@ GDB_VERSION = $(call qstrip,$(BR2_GDB_VERSION))
 GDB_SITE = $(BR2_GNU_MIRROR)/gdb
 GDB_SOURCE = gdb-$(GDB_VERSION).tar.xz
 
-# recent gdb versions (>= 10) have gdbserver moved at the top-level,
-# which requires a different build logic.
-ifeq ($(BR2_GDB_VERSION_10),y)
-GDB_GDBSERVER_TOPLEVEL = y
-endif
-
 ifeq ($(BR2_arc),y)
 GDB_SITE = $(call github,foss-for-synopsys-dwc-arc-processors,binutils-gdb,$(GDB_VERSION))
 GDB_SOURCE = gdb-$(GDB_VERSION).tar.gz
 GDB_FROM_GIT = y
-# recent gdb versions (>= 10) have gdbserver moved at the top-level,
-# which requires a different build logic.
-GDB_GDBSERVER_TOPLEVEL = y
 endif
 
 ifeq ($(BR2_csky),y)
@@ -35,7 +26,7 @@ GDB_CPE_ID_VENDOR = gnu
 
 # On gdb < 10, if you want to build only gdbserver, you need to
 # configure only gdb/gdbserver.
-ifeq ($(BR2_PACKAGE_GDB_DEBUGGER)$(GDB_GDBSERVER_TOPLEVEL),)
+ifeq ($(BR2_PACKAGE_GDB_DEBUGGER)$(BR2_PACKAGE_GDB_TOPLEVEL),)
 GDB_SUBDIR = gdb/gdbserver
 
 # When we want to build the full gdb, or for very recent versions of