fix(bkpyvenv): create relocatable venvs via --copies

Without the flag, `python -m venv` defaults to --symlinks on Linux,
so the resulting `$PREFIX/venv/bin/python` is an absolute symlink to
the python.org bottle's `/opt/python.org/v<X>/bin/python`. Any bottle
installed outside `/opt/` (eg. `/usr/local/pkgs/...` via pkgm) ends
up with a broken venv whose python entry point doesn't exist.

Pass `--copies` so the python binary is physically copied into the
venv instead of symlinked. This is the standard relocation pattern
for python venvs and matches what recipes that opt out of `bkpyvenv`
already do by hand (eg. pyqt5's recipe calls
`python -m venv --copies`).

Closes pkgxdev/pantry#8487.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: tannevaled

libexec/bkpyvenv

@@ -37,7 +37,13 @@ stage)
     poetry config virtualenvs.create true
     poetry config virtualenvs.in-project true
   else
-    python -m venv "$PREFIX"/venv
+    # --copies: copy the python binary into the venv instead of
+    # symlinking it. With the default --symlinks behavior the resulting
+    # `$PREFIX/venv/bin/python` is an absolute symlink to
+    # `/opt/python.org/v<ver>/bin/python`, which breaks any bottle
+    # installed somewhere other than /opt (eg. /usr/local/pkgs/...
+    # via pkgm). See pkgxdev/pantry#8487 for the original report.
+    python -m venv --copies "$PREFIX"/venv
   fi
   ;;
 seal)