buildman: Clarify the use of -V

This option outputs to the log file, not to the terminal. Clarify that in
the help, and add a mention of it in the README.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reported-by: Stephen Warren <swarren@wwwdotorg.org>
Reviewed-by: Stephen Warren <swarren@nvidia.com>

tools/buildman/README

@@ -612,7 +612,8 @@ The full build output in this case is available in:
    err:  Output from stderr, if any. Errors and warnings appear here.
 
    log:  Output from stdout. Normally there isn't any since buildman runs
-         in silent mode for now.
+         in silent mode. Use -V to force a verbose build (this passes V=1
+         to 'make')
 
    toolchain: Shows information about the toolchain used for the build.
 

tools/buildman/cmdline.py

@@ -85,7 +85,7 @@ def ParseArgs():
     parser.add_option('-v', '--verbose', action='store_true',
           default=False, help='Show build results while the build progresses')
     parser.add_option('-V', '--verbose-build', action='store_true',
-          default=False, help='Run make with V=1, showing all output')
+          default=False, help='Run make with V=1, logging all output')
     parser.add_option('-x', '--exclude', dest='exclude',
           type='string', action='append',
           help='Specify a list of boards to exclude, separated by comma')