util/genbuild: Correctly remove IASL warning

If IASL isn't installed, the genbuild script throws a confusing warning.
This can and should be ignored because toolchain.inc will find this and
provide a much better error message.

The trailing >/dev/null was probably intended to do this, but didn't
actually affect anything.

Adding quotes around the IASL command will make "" be the command that
tries to get run instead of `-v` when IASL isn't present. This will
always be a failure, whereas `-v` could theoretically be a valid
command.

Signed-off-by: Martin Roth <gaumless@gmail.com>
Change-Id: Ibff93db670766c4de21faa7553f2003450465407
Reviewed-on: https://review.coreboot.org/c/coreboot/+/76857
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Felix Singer <service+coreboot-gerrit@felixsinger.de>
diff --git a/util/genbuild_h/genbuild_h.sh b/util/genbuild_h/genbuild_h.sh
index 5e2fe7d..2bfcc4c 100755
--- a/util/genbuild_h/genbuild_h.sh
+++ b/util/genbuild_h/genbuild_h.sh
@@ -70,7 +70,7 @@
 if [ ! -x "${IASL}" ]; then
 	IASL=$(command -v iasl)
 fi
-IASLVERSION="$(${IASL} -v | grep version | sed 's/.*version //')" >/dev/null
+IASLVERSION="$("${IASL}" -v 2>/dev/null | grep version | sed 's/.*version //')"
 
 #Print out the information that goes into build.h
 printf "/* build system definitions (autogenerated) */\n"