Indirection for activation script since extension is important

Author: ksunden

activate.sh

@@ -0,0 +1 @@
+source $(dirname $0)/.binder/postBuild

pixi.toml

@@ -32,7 +32,7 @@ test = "bash ./test.sh"
 # Workaround overrides JupyterLab configuration (at the environment level) to
 # make double-clicking on a Jupytext Markdown file open that file as a
 # notebook. This is important for the development workflow for contributors.
-scripts = ["bash {$PIXI_PROJECT_ROOT}/.binder/postBuild"]
+scripts = ["activate.sh"]
 
 [feature.base.dependencies]
 python = ">=3.11"