vs2010backend: fix incompatibility with custom manifests

EmbedManifest seems to default to true, which creates a default manifest based
on other parameters (likewise defaults) and makes it impossible to supply your
own with CREATEPROCESS_MANIFEST_RESOURCE_ID. There is value to being able to do
this and no value to the default one, so this should be disabled.

mesonbuild/backend/vs2010backend.py

@@ -693,6 +693,8 @@ class Vs2010Backend(backends.Backend):
             if target_ext:
                 ET.SubElement(direlem, 'TargetExt').text = target_ext
 
+            ET.SubElement(direlem, 'EmbedManifest').text = 'false'
+
         return (root, type_config)
 
     def gen_run_target_vcxproj(self, target: build.RunTarget, ofname: str, guid: str) -> None: