buildenv: add API to get output archive

There's still room to improve this. But it is better than what we had.

Author: indygreg

cpython-unix/build.py

@@ -423,7 +423,7 @@ def process_setup_line(line, variant=None):
     # Extension variants are denoted by the presence of
     # Modules/VARIANT-<extension>-<variant>.data files that describe the
     # extension. Find those files and process them.
-    tf = build_env.get_archive("/build/out/python/build/Modules", as_tar=True)
+    tf = build_env.get_output_archive("python/build/Modules", as_tar=True)
 
     for ti in tf:
         basename = os.path.basename(ti.name)
@@ -639,7 +639,7 @@ def build_cpython(
         dest_path = BUILD / basename
 
         with dest_path.open("wb") as fh:
-            fh.write(build_env.get_archive("/build/out/python"))
+            fh.write(build_env.get_output_archive("python"))
 
 
 def main():

pythonbuild/buildenv.py

@@ -70,8 +70,8 @@ def get_tools_archive(self, dest, name):
         with open(dest, "wb") as fh:
             fh.write(data)
 
-    def get_archive(self, path, as_tar=False):
-        data = container_get_archive(self.container, path)
+    def get_output_archive(self, path, as_tar=False):
+        data = container_get_archive(self.container, "/build/out/%s" % path)
         data = io.BytesIO(data)
 
         if as_tar:
@@ -151,6 +151,17 @@ def get_tools_archive(self, dest, name):
         with dest.open("wb") as fh:
             create_tar_from_directory(fh, self.td / "out" / "tools")
 
+    def get_output_archive(self, path, as_tar=False):
+        data = io.BytesIO()
+        create_tar_from_directory(data, self.td / "out" / path)
+
+        data.seek(0)
+
+        if as_tar:
+            return tarfile.open(fileobj=data)
+        else:
+            return data.getvalue()
+
     def find_output_files(self, base_path, pattern):
         base = str(self.td / "out" / base_path)