buildman: Allow make-flags variables to include '-' and '_'
These characters are commonly used in variables, so permit them. Also
document the permitted characters.
Reported-by: Tom Rini <trini@ti.com>
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/buildman/README b/tools/buildman/README
index d20508f..68465b4 100644
--- a/tools/buildman/README
+++ b/tools/buildman/README
@@ -670,7 +670,9 @@
This will use 'make ENABLE_AT91_TEST=1 BUILD_TAG=442' for snapper9260
and 'make ENABLE_AT91_TEST=1 BUILD_TAG=443' for snapper9g45. A special
variable ${target} is available to access the target name (snapper9260 and
-snapper9g20 in this case). Variables are resolved recursively.
+snapper9g20 in this case). Variables are resolved recursively. Note that
+variables can only contain the characters A-Z, a-z, 0-9, hyphen (-) and
+underscore (_).
It is expected that any variables added are dealt with in U-Boot's
config.mk file and documented in the README.