genmultilib.awk: Use gsub instead of gensub.

	* config/avr/genmultilib.awk: Use gsub instead of gensub.

From-SVN: r248357

gcc/ChangeLog

+2017-05-23  Georg-Johann Lay  <avr@gjlay.de>
+
+	* config/avr/genmultilib.awk: Use gsub instead of gensub.
+
 2017-05-22  Michael Meissner  <meissner@linux.vnet.ibm.com>
 
 	PR target/80718

gcc/config/avr/genmultilib.awk

@@ -123,7 +123,7 @@ BEGIN {
 	have[opts] = 1
 	# Some special handling for the default mmcu: Remove a
 	# leading "mmcu=avr2/" in order not to confuse genmultilib.
-	opts = gensub (/mmcu=avr2\//, "", 1, opts)
+	gsub (/^mmcu=avr2\//, "", opts)
 	if (opts != "mmcu=avr2")
 	    m_required = m_required " \\\n\t" opts
     }