python - sql.h not found when installing PyODBC on Heroku -

i'm trying install pyodbc on heroku, fatal error: sql.h: no such file or directory in logs when pip runs. how fix error?

to follow on answer below...

example ubuntu:

sudo apt-get install unixodbc unixodbc-dev 

example centos:

sudo yum install unixodbc-devel 

on windows:

conn = pyodbc.connect('driver={sql server};server=yourserver.yourcompany.com;database=yourdb;uid=user;pwd=password') 

on linux:

conn = pyodbc.connect('driver={freetds};server=yourserver.yourcompany.com;port=1433;database=yourdb;uid=user;pwd=password;tds_version=7.2')