cmake: Organize targets into folders

Enabling CMake's USE_FOLDERS option and adding the FOLDER property to
targets allows some IDEs to list the targets in an organized
hierarchy of folders.

src/nvim/CMakeLists.txt

@@ -470,10 +470,12 @@ if(WIN32)
   file(WRITE ${PROJECT_BINARY_DIR}/external_blobs.cmake ${EXTERNAL_BLOBS_SCRIPT})
   add_custom_target(external_blobs
     COMMAND ${CMAKE_COMMAND} -P ${PROJECT_BINARY_DIR}/external_blobs.cmake)
+  set_target_properties(external_blobs PROPERTIES FOLDER deps)
   add_dependencies(nvim_runtime_deps external_blobs)
 else()
   add_custom_target(nvim_runtime_deps)  # Stub target to avoid CMP0046.
 endif()
+set_target_properties(nvim_runtime_deps PROPERTIES FOLDER deps)
 
 add_library(
   libnvim
@@ -585,6 +587,7 @@ foreach(hfile ${NVIM_HEADERS})
       TARGET ${texe}
       APPEND PROPERTY INCLUDE_DIRECTORIES ${LUA_PREFERRED_INCLUDE_DIRS}
     )
+    set_target_properties(${texe} PROPERTIES FOLDER test)
 
     list(FIND NO_SINGLE_CHECK_HEADERS "${relative_path}" hfile_exclude_idx)
     if(${hfile_exclude_idx} EQUAL -1)

src/nvim/po/CMakeLists.txt

@@ -55,6 +55,7 @@ if(HAVE_WORKING_LIBINTL AND GETTEXT_FOUND AND XGETTEXT_PRG AND ICONV_PRG)
     DEPENDS ${NVIM_SOURCES})
 
   add_custom_target(potfile DEPENDS ${NVIM_POT})
+  set_target_properties(potfile PROPERTIES FOLDER po)
 
   set(LANGUAGE_MO_FILES)
   set(UPDATE_PO_TARGETS)
@@ -91,6 +92,7 @@ if(HAVE_WORKING_LIBINTL AND GETTEXT_FOUND AND XGETTEXT_PRG AND ICONV_PRG)
       COMMENT "Checking ${name}.po"
       VERBATIM
       DEPENDS ${poFile})
+    set_target_properties(check-po-${name} PROPERTIES FOLDER po/check)
   endmacro()
 
   macro(BuildPoIconvGenericWithCharset
@@ -182,7 +184,9 @@ if(HAVE_WORKING_LIBINTL AND GETTEXT_FOUND AND XGETTEXT_PRG AND ICONV_PRG)
 
     BuildMo(${LANGUAGE})
   endforeach()
+  set_target_properties(${UPDATE_PO_TARGETS} PROPERTIES FOLDER po/update)
 
   add_custom_target(translations ALL DEPENDS ${LANGUAGE_MO_FILES})
   add_custom_target(update-po DEPENDS ${UPDATE_PO_TARGETS})
+  set_target_properties(translations update-po PROPERTIES FOLDER po)
 endif()