Place each chicken piece between 2 sheets of heavy-duty plastic wrap, and flatten to 1/4-inch thickness, using a meat mallet or rolling pin. Combine 1/4 teaspoon of salt, garlic powder, and next 4 ingredients; sprinkle over both sides of chicken, and set aside.
Coat a large nonstick skillet with cooking spray; add margarine, and place over medium-high heat until margarine melts. Add the chicken, and cook 1 1/2 minutes on each side or until lightly browned. Remove from skillet; set aside.
Add leeks and garlic to skillet; cook over medium-high heat 3 minutes or until tender. Add chicken broth and next 3 ingredients; bring to a boil. Break linguine into 2-inch pieces; add linguine and chicken to skillet. Cover and cook over medium-low heat 15 minutes or until pasta is tender.