Use source Makefile from checked out code instead of build-X

[SaitTalhaNisanci]

We can possibly use the Makefile from the checked out code in CircleCI, currently we are using the makefile from:

the-process/circleci/images/exttester/files/sbin/install-and-test-ext

Line 17 in 21c4335

gosu circleci make -C "${CIRCLE_WORKING_DIRECTORY}/build-${PG_MAJOR}/src/test/regress" "${@}" || status=$?

This would enable us to not copy the build-X artifacts in our workflows.