improve CmdStan installation process: instructions, scripts, package installers

[mitzimorris]

Summary:

This issue is a place to discuss pain points and solutions for the problem of installing a CmdStan release tar.gz file.

This solution doesn't include installing CmdStan from GitHub; although documentation for that process should be reviewed and corrected/updated/expanded as needed.

Description:

Pain points:

• users don't have system install permissions
• users don't have requisite toolchain installed on their system.
• OS updates cause problems for existing installation by changing the toolchain
• CmdStan library and binaries take non-trivial time to compile - installation on a wimpy machine is slow.
• In order to speed up Stan model compile time, libraries, headers, and command.o are precompiled by the Makefile build task; but the latter two need to be recompiled if threading or processing lib changes.

Components of a solution:

1. Provide developer toolchain: c++ compiler + GNU-make + unix utilities used by Makefile
   • MacOSX: run xcode-select vs. install xcode command line tools in Stan-specific place
   • Linux: do all versions of Linux have GNU-make? if so, clang binaries as above
   • Windows - fork RTools and build Stan-specific version
2. Provide pre-compiled binaries for CmdStan release, assuming vanilla threading and processor
3. Provide user with install options:
   • instructions
   • script
   • pkg installer utility

Platforms we need to support:

• MacOS - how far back?
• Linux: redhat (RHEL, Fedora, CentOS - rpm package manager), debian (Ubuntu - dpkg manager)
• Windows 7, 10

Stan Makefile calls to shell and os utilities: echo,uname,expr,where,find,curl, also need Python to run tests

[mitzimorris]

update: xcode is open source and can be downloaded from Apple here: https://developer.apple.com/download/more/?=command%20line%20tools.

• size of dmg file is 451 MB
• compare to RStudio installer dmg file - size is 152 MB - RStudio installer will invoke xcode-select if it can't find it.