Ports: Don't unset {HOME,USER,TERM,PATH}

These are required for the `dev` environment (or more precisely, `git`)
to work.

Ports/.strip_env.sh

@@ -1,6 +1,10 @@
 #!/usr/bin/env bash
 
 exec env -i SERENITY_STRIPPED_ENV=1 \
+    HOME="${HOME}" \
+    USER="${USER}" \
+    TERM="${TERM}" \
+    PATH="${PATH}" \
     MAKEJOBS="${MAKEJOBS:-}" \
     IN_SERENITY_PORT_DEV="${IN_SERENITY_PORT_DEV:-}" \
     SERENITY_ARCH="${SERENITY_ARCH:-}" \