[#13254] YSQL: add pgtap to build

Summary:
This diff integrates pgtap extension to build by adding it to third-party directory makefile
Jira: DB-2904

Test Plan: jenkins: compile-only

Reviewers: hsunder, jason

Reviewed By: jason

Subscribers: yql

Differential Revision: https://phorge.dev.yugabyte.com/D36772

src/postgres/third-party-extensions/Makefile

@@ -9,6 +9,7 @@ DIRS = \
 	postgresql-hll \
 	pg_partman \
 	wal2json \
+	pgtap \
 
 BUILDDIRS = $(DIRS:%=build-%)
 INSTALLDIRS = $(DIRS:%=install-%)