verify tool variable validity before using it.

If the toolchain for a stage/architecture wasn't present, we'd call the
shell with '-v', generating an ugly warning:

/bin/sh: - : invalid option
Usage:  /bin/sh [GNU long option] [option] ...
        /bin/sh [GNU long option] [option] script-file ...
GNU long options:

Change-Id: Icd6d7a00083ee1695591ff96da36b7868be0c2f0
Signed-off-by: Martin Roth <>
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <>
1 file changed