ci: Add test coverage of different pg_upgrade modes

Run freebsd with --link and macos with --clone, to get some coverage
of the non-default modes.

Author: Justin Pryzby <pryzby@telsasoft.com>
Discussion: https://www.postgresql.org/message-id/flat/20220528153741.GK19626@telsasoft.com

.cirrus.tasks.yml

@@ -138,6 +138,8 @@ task:
     CPPFLAGS: -DRELCACHE_FORCE_RELEASE -DCOPY_PARSE_PLAN_TREES -DWRITE_READ_PARSE_PLAN_TREES -DRAW_EXPRESSION_COVERAGE_TEST -DENFORCE_REGRESSION_TEST_NAME_RESTRICTIONS
     CFLAGS: -Og -ggdb
 
+    PG_TEST_PG_UPGRADE_MODE: --link
+
   <<: *freebsd_task_template
 
   depends_on: SanityCheck
@@ -431,6 +433,8 @@ task:
     CFLAGS: -Og -ggdb
     CXXFLAGS: -Og -ggdb
 
+    PG_TEST_PG_UPGRADE_MODE: --clone
+
   <<: *macos_task_template
 
   depends_on: SanityCheck