Kconfig: Fix missing help text in DEVEL config menu

This patch completes missing help text for some options under CONFIG_DEVEL.

Provides help for BINARY_FOLDER and DOWNLOAD_FOLDER, and reduces ambiguity in
the help for BUILD_SUFFIX with an example.

Signed-off-by: Andrew McDonnell <bugs@andrewmcdonnell.net>

SVN-Revision: 42520

config/Config-devel.in

@@ -15,10 +15,19 @@ menuconfig DEVEL
 	config BINARY_FOLDER
 		string "Binary folder" if DEVEL
 		default ""
+		help
+		  Store built firmware images and filesystem images in this directory.
+		  If not set, uses './bin/$(BOARD)'
 
 	config DOWNLOAD_FOLDER
 		string "Download folder" if DEVEL
 		default ""
+		help
+		  Store downloaded source bundles in this directory.
+		  If not set then defaults to './dl', which is removed by operations such as
+		  'git clean -xdf' or 'make distclean'.
+		  This option is useful if you have a low bandwidth Internet connection, and by
+		  setting a path outside the OpenWRT tree downloads will be saved.
 
 	config LOCALMIRROR
 		string "Local mirror for source packages" if DEVEL
@@ -31,10 +40,12 @@ menuconfig DEVEL
 		  Automatically rebuild packages when their files change.
 
 	config BUILD_SUFFIX
-		string "Build suffix to append to the BUILD_DIR variable" if DEVEL
+		string "Build suffix to append to the target BUILD_DIR variable" if DEVEL
 		default ""
 		help
-		  Build suffix to append to the BUILD_DIR variable, i.e: build_dir_suffix.
+		  Build suffix to append to the BUILD_DIR variable, i.e: './build_dir/{target-build-dir}_$(BUILD_SUFFIX)'.
+		  This allows you to switch to a different .config whilst retaining all the build
+		  objects generated by the first .config
 
 	config TARGET_ROOTFS_DIR
 		string "Override the default TARGET_ROOTFS_DIR variable" if DEVEL