Set PYTHONEXECUTABLE to be the runfiles interpreter path

Author: arrdem

py/tools/py/src/activate.tmpl

@@ -61,6 +61,12 @@ deactivate nondestructive
 VIRTUAL_ENV="$(dirname "$(dirname "${BASH_SOURCE}")")"
 export VIRTUAL_ENV
 
+# HACK: (Ab)use the MacOS $PYTHONEXECUTABLE to record the `.runfiles`-relative
+# interpreter path. This helps us avoid issues with the interpreter's path being
+# `realpath`-ed in such a way that it escapes the `.runfiles` tree.
+PYTHONEXECUTABLE="${VIRTUAL_ENV}/bin/python"
+export PYTHONEXECUTABLE
+
 # unset PYTHONHOME if set
 # this will fail if PYTHONHOME is set to the empty string (which is bad anyway)
 # could use `if (set -u; : $PYTHONHOME) ;` in bash.