build: various build improvements

- remove "ran-" prefix from touch files as it's redundant since the
  they're already in the directory named `touches`.
- Include `contrib` when formatting with `make formatlua`.
- Use TARGET_FILE generator expression instead of assuming the
  executable location.
- reuse logic that determines whether to use lua or luajit.
- add translations to the `nvim` target.

Makefile improvements:
- rename variable `CMAKE_PRG` to `CMAKE` to make it more consistent with
  the builtin `MAKE` variable.
- stop propagating flags to generator. Users should use cmake for
  non-standard use cases.
- remove `+` prefix from targets. If the user for whatever reason wants
  to dry-run a target then they should be able to.

contrib/minimal.lua

@@ -1,10 +1,10 @@
 -- Run this file as `nvim --clean -u minimal.lua`
 
-for name, url in pairs{
+for name, url in pairs {
   -- ADD PLUGINS _NECESSARY_ TO REPRODUCE THE ISSUE, e.g:
   -- some_plugin = 'https://github.com/author/plugin.nvim'
 } do
-  local install_path = vim.fn.fnamemodify('nvim_issue/'..name, ':p')
+  local install_path = vim.fn.fnamemodify('nvim_issue/' .. name, ':p')
   if vim.fn.isdirectory(install_path) == 0 then
     vim.fn.system { 'git', 'clone', '--depth=1', url, install_path }
   end