buildman: Only print toolchain probing with -v

At present --list-tool-chains prints a lot of information about the
toolchain-probing process. This is generally not very interesting.
Update buildman to print this only if --list-tool-chains is given
with -v.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/buildman/cmdline.py b/tools/buildman/cmdline.py
index 49a8a13..93d09ca 100644
--- a/tools/buildman/cmdline.py
+++ b/tools/buildman/cmdline.py
@@ -66,7 +66,7 @@
     parser.add_option('-l', '--list-error-boards', action='store_true',
           default=False, help='Show a list of boards next to each error/warning')
     parser.add_option('--list-tool-chains', action='store_true', default=False,
-          help='List available tool chains')
+          help='List available tool chains (use -v to see probing detail)')
     parser.add_option('-n', '--dry-run', action='store_true', dest='dry_run',
           default=False, help="Do a dry run (describe actions, but do nothing)")
     parser.add_option('-N', '--no-subdirs', action='store_true', dest='no_subdirs',
diff --git a/tools/buildman/control.py b/tools/buildman/control.py
index 96f8ccf..c900211 100644
--- a/tools/buildman/control.py
+++ b/tools/buildman/control.py
@@ -164,7 +164,7 @@
 
     if no_toolchains:
         toolchains.GetSettings()
-        toolchains.Scan(options.list_tool_chains)
+        toolchains.Scan(options.list_tool_chains and options.verbose)
     if options.list_tool_chains:
         toolchains.List()
         print