Improve packaged Linux binary performance (#1755)
Improve packaged Linux binary performance (#1755)

In order to address problems on older CPUs with "illegal instruction"
errors, we set the target CPU to x86-64 for Deb and RPM release builds.
Original issue is #1682 and the PR to implement was #1686.

As part of #1682, we discussed that we should also build using
-mtune=intel to get better performance.
sgebbie/ponyc,ponylang/ponyc,Theodus/ponyc,mkfifo/ponyc,cquinn/ponyc,Perelandric/ponyc,ponylang/ponyc,CausalityLtd/ponyc,boemmels/ponyc,kulibali/ponyc,mkfifo/ponyc,sgebbie/ponyc,jemc/ponyc,mkfifo/ponyc,sgebbie/ponyc,kulibali/ponyc,cquinn/ponyc,mkfifo/ponyc,Perelandric/ponyc,Praetonus/ponyc,CausalityLtd/ponyc,Praetonus/ponyc,jemc/ponyc,Perelandric/ponyc,cquinn/ponyc,dipinhora/ponyc,boemmels/ponyc,boemmels/ponyc,sgebbie/ponyc,Theodus/ponyc,sgebbie/ponyc,CausalityLtd/ponyc,Praetonus/ponyc,dipinhora/ponyc,jemc/ponyc,ponylang/ponyc,dipinhora/ponyc,cquinn/ponyc,Theodus/ponyc,Theodus/ponyc,kulibali/ponyc,mkfifo/ponyc,Perelandric/ponyc,boemmels/ponyc,Praetonus/ponyc,Theodus/ponyc,boemmels/ponyc,kulibali/ponyc,Perelandric/ponyc