scripts/mkcompile_h: don't test for hardcoded paths

Don't test for /bin/{dnsdomainname,domainname}, simply try to execute
the command and check if it returned something.
Reported-by: Glenn Sommer <glemsom@gmail.com>
Acked-by: WANG Cong <xiyou.wangcong@gmail.com>
Tested-by: Glenn Sommer <glemsom@gmail.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>

scripts/mkcompile_h

@@ -67,9 +67,8 @@ UTS_TRUNCATE="cut -b -$UTS_LEN"
   echo \#define LINUX_COMPILE_BY \"`whoami`\"
   echo \#define LINUX_COMPILE_HOST \"`hostname | $UTS_TRUNCATE`\"
 
-  if [ -x /bin/dnsdomainname ]; then
-    domain=`dnsdomainname 2> /dev/null`
-  elif [ -x /bin/domainname ]; then
+  domain=`dnsdomainname 2> /dev/null`
+  if [ -z "$domain" ]; then
     domain=`domainname 2> /dev/null`
   fi