gnu: python-setuptools-scm-git-archive: Don't install duplicate egginfo.

* gnu/packages/python-xyz.scm (python-setuptools-scm-git-archive)[arguments]:
New field.

gnu/packages/python-xyz.scm

@@ -19786,6 +19786,16 @@ services.")
         (base32
          "1nii1sz5jq75ilf18bjnr11l9rz1lvdmyk66bxl7q90qan85yhjj"))))
     (build-system python-build-system)
+    (arguments
+     '(#:phases (modify-phases %standard-phases
+                  (add-after 'unpack 'dont-install-defunct-egginfo
+                    (lambda _
+                      ;; When a ".git" directory is missing, the setup.py
+                      ;; script invokes setuptools.setup twice, once with
+                      ;; "0" as the version.  Prevent that.
+                      (substitute* "setup.py"
+                        (("if not isdir\\('\\.git'\\):")
+                         "if False:")))))))
     (native-inputs
      (list python-pytest))
     (propagated-inputs