build: fix centos-8 'make install-deps' enable PowerTools repo

build: fix centos-8 'make install-deps' enable PowerTools repo

- The name of the powertools repo was changed [0]
  in centos-8 from 'PowerTools' to 'powertools'.
  Retrieve the correct name from 'dnf repolist all'
  instead of hard coding it.

[0] https://git.centos.org/rpms/centos-repos/c/b759b17557b9577e8ea156740af0249ab1a22d70

Type: fix

Signed-off-by: Dave Wallace <dwallacelf@gmail.com>
Change-Id: Ic1402e671eb1d70dec429bab82ad18d8251f4eef
(cherry picked from commit 1affb31ef528dcbc90b718bd70a9882a4225a385)