Oracle Spool using Dynamic SQL

I'm trying to pass a dynamic SQL statement to spool out to a text file using SQL*Plus, but I can't seem to execute the select statement I'm generating.

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COLUMN gen_sql   NEW_VALUE gen_sql_
SELECT 'SELECT * FROM USER_TAB_COLS WHERE ROWNUM < 10' gen_sql_ FROM DUAL;

SPOOL 'myfilename.csv'

EXECUTE IMMEDIATE &gen_sql_

SPOOL OFF
/

I can't seem to use EXECUTE IMMEDIATE. Is there another way to execute the results of the select statement??

MORE DETAIL:

I have a set of views whose output I'd like to generate as formatted CSV files. I'm using dynamic SQL to create the formatting essentially. I generate something similar to:

SELECT TRIM(col1)||','||TRIM(col2)...FROM {myview}

I'm using the following to generate it this way:

COLUMN gen_sql   NEW_VALUE gen_sql_
SELECT 'SELECT ' || LISTAGG ('TRIM('||COLUMN_NAME||')', '||'',''|| ') 
     WITHIN GROUP (ORDER BY COLUMN_ID) gen_sql FROM...

Anyway, I'm able generate this SQL statement and store into a SQL*PLUS variable, but I just need to execute it after the SPOOL statement so that it will print to the file. I'm not sure how to execute it. Normal statements work, such as:

SPOOL 'myfilename.csv'
SELECT 1 col1 FROM DUAL;
SPOOL OFF
/

So, it would seem reasonable that I could something similar but executing the contents of my variable like:

SPOOL 'myfilename.csv'
--- RUN MY DYNAMIC SQL ----
SPOOL OFF
/

via Chebli Mohamed