futility: Improve help messages

This provides help messages for the futility commands similar to
the way git does. These show the available commands:

  futility
  futility help
  futility --help

While these show help for a specific command:

  futility help COMMAND
  futility --help COMMAND
  futility COMMAND --help

BUG=none
BRANCH=ToT
TEST=manual

make runtests

And manually look at help messages for each command.

Change-Id: I1126471e242784c6ca7a2f11694fa7c505d833e8
Signed-off-by: Bill Richardson <wfrichar@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/219528
Reviewed-by: Randall Spangler <rspangler@chromium.org>
diff --git a/Makefile b/Makefile
index d091e18..b65c692 100644
--- a/Makefile
+++ b/Makefile
@@ -1046,7 +1046,7 @@
 	@$(PRINTF) "    GEN           $(subst ${BUILD}/,,$@)\n"
 	${Q}rm -f $@ $@_t $@_commands
 	${Q}mkdir -p ${BUILD}/gen
-	${Q}grep -hoRE '^DECLARE_FUTIL_COMMAND\([^,]+' $^ -R \
+	${Q}grep -hoRE '^DECLARE_FUTIL_COMMAND\([^,]+' $^ \
 		| sed 's/DECLARE_FUTIL_COMMAND(\(.*\)/_CMD(\1)/' \
 		| sort >>$@_commands
 	${Q}echo '#define _CMD(NAME) extern const struct' \