* config.guess (set_cc_for_build): Prevent multiple calls by

chechking if $tmp is already set. We can't check CC_FOR_BUILD as
	the user may set it externally. Thanks to Torbjörn Granlund for
	the bug report.

config.guess

@@ -99,6 +99,8 @@ tmp=
 trap 'test -z "$tmp" || rm -fr "$tmp"' 0 1 2 13 15
 
 set_cc_for_build() {
+    # prevent multiple calls if $tmp is already set
+    test "$tmp" && return 0
     : "${TMPDIR=/tmp}"
     # shellcheck disable=SC2039
     { tmp=`(umask 077 && mktemp -d "$TMPDIR/cgXXXXXX") 2>/dev/null` && test -n "$tmp" && test -d "$tmp" ; } ||