Exclude Power8 before MongoDB 3.2, as it's not supported there yet

Author: derickr

.evergreen/config.yml

@@ -674,13 +674,15 @@ buildvariants:
 
 - matrix_name: "mongo-30-php5"
   matrix_spec: {"os-php5": "*", "versions": ["3.0", "3.2", "3.4"], "php-versions": "5.6" }
+  exclude_spec: {"os-php5": "rhel71-power8", "versions": "3.0", "php-versions": "5.6"}
   display_name: "${versions}/${php-versions} — ${os-php5}"
   tasks:
      - name: "test-standalone-old"
      - name: "test-replicaset-old"
 
 - matrix_name: "mongo-30-php7"
   matrix_spec: {"os-php7": "*", "versions": ["3.0", "3.2", "3.4"], "php-versions": "7.2" }
+  exclude_spec: {"os-php7": "rhel71-power8", "versions": "3.0", "php-versions": "7.2"}
   display_name: "${versions}/${php-versions} — ${os-php7}"
   tasks:
      - name: "test-standalone-old"