meson.build: Make radio_tool and objcopy optional

meson.build

@@ -180,23 +180,27 @@ foreach t : targets
 
   if t['flashable']
 
-    bin = custom_target(name+'_bin',
-      output : name+'_bin',
-      input : exe,
-      command : [objcopy, '-O', 'binary', '@INPUT@', '@OUTPUT@'])
+    if objcopy.found()
+      bin = custom_target(name+'_bin',
+        output : name+'_bin',
+        input : exe,
+        command : [objcopy, '-O', 'binary', '@INPUT@', '@OUTPUT@'])
 
-    wrap = custom_target(name+'_wrap',
-      output : name+'_wrap',
-      input : bin,
-      command : [radio_tool,
-                 '--wrap',
-                 '-o', '@OUTPUT@',
-                 '-r', t['wrap'],
-                 '-s', t['load_addr']+':@INPUT@'])
+      if radio_tool.found()
+        wrap = custom_target(name+'_wrap',
+          output : name+'_wrap',
+          input : bin,
+          command : [radio_tool,
+                     '--wrap',
+                     '-o', '@OUTPUT@',
+                     '-r', t['wrap'],
+                     '-s', t['load_addr']+':@INPUT@'])
 
-    custom_target(name+'_flash',
-      input : wrap,
-      output : name+'_flash',
-      command : [radio_tool, '-d', '0', '-f', '-i', '@INPUT@'])
+        custom_target(name+'_flash',
+          input : wrap,
+          output : name+'_flash',
+          command : [radio_tool, '-d', '0', '-f', '-i', '@INPUT@'])
+      endif
+    endif
   endif
 endforeach