buildman: Ignore blank lines during size checks

Today when parsing the .sizes files we get a warning about an invalid
line in the file as it's blank.  Solve this by checking that we have a
non-blank line prior to processing.

Cc: Simon Glass <sjg@chromium.org>
Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

tools/buildman/builder.py

@@ -577,7 +577,8 @@ class Builder:
         sym = {}
         for line in fd.readlines():
             try:
-                size, type, name = line[:-1].split()
+                if line.strip():
+                    size, type, name = line[:-1].split()
             except:
                 Print("Invalid line in file '%s': '%s'" % (fname, line[:-1]))
                 continue