utils: Reduce the number of calls to the "dirname" command

utils.bbclass contains create_cmdline_wrapper() function that
creates wrapper script with additional arguments for any passed
"$cmd" command, and uses several calls to "dirname".

Because "dirname" is an external command, in cases of lots of
calls to wrapped "$cmd", each call of "dirname" will incur
significant overhead.

There are three same calls to "dirname": one for saving it`s
output to "realdir" variable, and other two in "exec" command.
So last two "dirname" calls can be replaced with cached value
from "realdir" variable.

(From OE-Core rev: 4b9cf2c80fd14386e0b88a2e6c40a9fa3f1ae0f7)

Signed-off-by: Oleksandr Popovych <opopovyc@cisco.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/utils.bbclass

@@ -214,7 +214,7 @@ create_cmdline_wrapper () {
 #!/bin/bash
 realpath=\`readlink -fn \$0\`
 realdir=\`dirname \$realpath\`
-exec -a \`dirname \$realpath\`/$cmdname \`dirname \$realpath\`/$cmdname.real $cmdoptions "\$@"
+exec -a \$realdir/$cmdname \$realdir/$cmdname.real $cmdoptions "\$@"
 END
 	chmod +x $cmd
 }