librz/arch/alpha: build only for Capstone > 5 (#4735)

librz/arch/meson.build

@@ -6,7 +6,6 @@ subdir('platforms')
 arch_plugins_list = [
   '6502',
   '8051',
-  'alpha_cs',
   'amd29k',
   'arm_as',
   'arm_cs',
@@ -64,7 +63,6 @@ arch_plugins_list = [
 arch_plugin_sources = [
   'p/arch_6502.c',
   'p/arch_8051.c',
-  'p/arch_alpha.c',
   'p/arch_amd29k.c',
   'p/arch_arm_as.c',
   'p/arch_arm_cs.c',
@@ -326,11 +324,13 @@ endif
 if capstone_dep.version() == 'next'
   # plugins
   arch_plugins_list += [
+    'alpha_cs',
     'xtensa_cs',
   ]
 
   # plugins sources
   arch_plugin_sources += [
+    'p/arch_alpha.c',
     'p/arch_xtensa_cs.c',
   ]