Execute immediate with dynamic sql in Google BigQuery

Question

Following this question, I was trying to create a dynamic SQL statement with a pivot table and a CTE in Google BigQuery.

This worked straight of the box (with CTE and pivot):

with Produce AS (
  SELECT 'Kale' as product, 51 as sales, 'Q1' as quarter UNION ALL
  SELECT 'Kale', 23, 'Q2' UNION ALL
  SELECT 'Kale', 45, 'Q3' UNION ALL
  SELECT 'Kale', 3, 'Q4' UNION ALL
  SELECT 'Apple', 77, 'Q1' UNION ALL
  SELECT 'Apple', 0, 'Q2' UNION ALL
  SELECT 'Apple', 25, 'Q3' UNION ALL
  SELECT 'Apple', 2, 'Q4')
SELECT * FROM
  (SELECT product, sales, quarter FROM Produce)
  PIVOT(SUM(sales) FOR quarter IN ('Q1', 'Q2', 'Q3', 'Q4'))

Then I tried to modify it to include the dynamic SQL using execute immediate:

execute immediate( 
    """ 
     with Produce as (
  SELECT 'Kale' as product, 51 as sales, 'Q1' as quarter UNION ALL
  SELECT 'Kale', 23, 'Q2' UNION ALL
  SELECT 'Kale', 45, 'Q3' UNION ALL
  SELECT 'Kale', 3, 'Q4' UNION ALL
  SELECT 'Apple', 77, 'Q1' UNION ALL
  SELECT 'Apple', 0, 'Q2' UNION ALL
  SELECT 'Apple', 25, 'Q3' UNION ALL
  SELECT 'Apple', 2, 'Q4'
  )            
  select '''
    select * 
    from (select product, sales, quarter from Produce)
    pivot(sum(sales) for quarter in ("''' ||  string_agg(distinct quarter, '", "' order by quarter)  || '''"))
  '''
  from Produce
  """
);

My issue is, this above prints out the query instead of executing it.

How can I modify it to actually get it to execute and get me the sample results using the data in the CTE?