New install procedure for PostgreSQL 9.4+ for RHEL 7.7

[fabiocosta0305]

Please, provide new instructions on how to install PostgreSQL 9.4 or better for RHEL 7.7

The ones from https://github.com/linux-on-ibm-z/docs/wiki/Building-PostgreSQL-9.4-on-RHEL7 results on RPM complaining on libssl.1.0.0 and libcrypto.1.0.0...

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[fabiocosta0305]

Adding an output after doing rpmbuild and doing rpm -i the new packages

error: Failed dependencies:
	libcrypto.so.1.0.0()(64bit) is needed by postgresql95-contrib-9.5.21-1PGDG.el7.s390x
	libssl.so.1.0.0()(64bit) is needed by postgresql95-contrib-9.5.21-1PGDG.el7.s390x
	libcrypto.so.1.0.0()(64bit) is needed by postgresql95-libs-9.5.21-1PGDG.el7.s390x
	libssl.so.1.0.0()(64bit) is needed by postgresql95-libs-9.5.21-1PGDG.el7.s390x
	libcrypto.so.1.0.0()(64bit) is needed by postgresql95-server-9.5.21-1PGDG.el7.s390x
	libssl.so.1.0.0()(64bit) is needed by postgresql95-server-9.5.21-1PGDG.el7.s390x

[Nayana-ibm]

@fabiocosta0305 Latest version12.x build instructions are here: https://github.com/linux-on-ibm-z/docs/wiki/Building-PostgreSQL-12.x . This includes RHEL 7.7 as well.