target/or1k: Build 'gdbstub.c' once for system single binary

There is a single qemu-system-or1k binary, but by moving
'gdbstub.c' in the target_common_system_arch[] source set
the resulting object can be linked into a single qemu-sytem
binary.

Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20260219191955.83815-43-philmd@linaro.org>

target/or1k/meson.build

@@ -8,18 +8,25 @@ or1k_ss.add(files(
   'exception.c',
   'exception_helper.c',
   'fpu_helper.c',
-  'gdbstub.c',
   'interrupt_helper.c',
   'sys_helper.c',
   'translate.c',
 ))
 
+or1k_user_ss = ss.source_set()
+or1k_user_ss.add(files('gdbstub.c'))
+
 or1k_common_system_ss = ss.source_set()
-or1k_common_system_ss.add(files(
+or1k_common_system_ss.add(files('gdbstub.c'))
+
+or1k_system_ss = ss.source_set()
+or1k_system_ss.add(files(
   'interrupt.c',
   'machine.c',
   'mmu.c',
 ))
 
 target_arch += {'or1k': or1k_ss}
+target_user_arch += {'or1k': or1k_user_ss}
+target_system_arch += {'or1k': or1k_system_ss}
 target_common_system_arch += {'or1k': or1k_common_system_ss}