RPM build should fail if required tooling is missing

[NikolaMilosavljevic]

Currently, if the build is supposed to produce RPM packages, but the tooling (i.e. fpm) is missing, a message will be logged and the build will skip the RPM package generation:

installer/src/redist/targets/GenerateRPMs.targets

Lines 313 to 316 in bbf4421

	<!-- Workaround for Jenkins machines that don't have the necessary packages https://github.com/dotnet/core-setup/issues/2260 -->
	<Message Condition=" '$(FPMPresent)' != 'True' "
	Text="FPM tool Not found, RPM packages will not be built."
	Importance="High"/>

The build should fail.

This should be fixed in all supported 8.0 and 9.0 branches.

[NikolaMilosavljevic]

This is now complete - changes were made in both installer (8.0) and sdk (9.0).