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.

cmake/Util.cmake

@@ -89,7 +89,7 @@ function(add_glob_target)
   endif()
 
   if(ARG_TOUCH_STRATEGY STREQUAL SINGLE)
-    set(touch_file ${TOUCHES_DIR}/ran-${ARG_TARGET})
+    set(touch_file ${TOUCHES_DIR}/${ARG_TARGET})
     add_custom_command(
       OUTPUT ${touch_file}
       COMMAND ${CMAKE_COMMAND} -E touch ${touch_file}
@@ -103,7 +103,7 @@ function(add_glob_target)
     foreach(f ${ARG_FILES})
       string(REGEX REPLACE "^${PROJECT_SOURCE_DIR}/" "" tf ${f})
       string(REGEX REPLACE "[/.]" "-" tf ${tf})
-      set(touch_file ${touch_dir}/ran-${tf})
+      set(touch_file ${touch_dir}/${tf})
       add_custom_command(
         OUTPUT ${touch_file}
         COMMAND ${CMAKE_COMMAND} -E touch ${touch_file}
@@ -133,7 +133,7 @@ function(add_glob_target)
       file(MAKE_DIRECTORY ${td})
       string(REGEX REPLACE "^${PROJECT_SOURCE_DIR}/" "" tf ${touch_dir})
       string(REGEX REPLACE "[/.]" "-" tf ${tf})
-      set(touch_file ${td}/ran-${tf})
+      set(touch_file ${td}/${tf})
 
       add_custom_command(
         OUTPUT ${touch_file}