Add compatibility for busybox mktemp

Busybox's mktemp requires at least six X's in the template, causing
the current sed --in-place check to fail because the file does not
exist. This change adds additional X's to mktemp templates that do
not already have at least six X's in them.

Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Quentin Zdanis <zdanisq@gmail.com>
Closes #11269

config/always-sed.m4

@@ -4,7 +4,7 @@ dnl #
 AC_DEFUN([ZFS_AC_CONFIG_ALWAYS_SED], [
 	AC_REQUIRE([AC_PROG_SED])dnl
 	AC_CACHE_CHECK([for sed --in-place], [ac_cv_inplace], [
-		tmpfile=$(mktemp conftest.XXX)
+		tmpfile=$(mktemp conftest.XXXXXX)
 		echo foo >$tmpfile
 		AS_IF([$SED --in-place 's#foo#bar#' $tmpfile 2>/dev/null],
 		      [ac_cv_inplace="--in-place"],

config/deb.am

@@ -53,7 +53,7 @@ deb-utils: deb-local rpm-utils-initramfs
 ## Arguments need to be passed to dh_shlibdeps. Alien provides no mechanism
 ## to do this, so we install a shim onto the path which calls the real
 ## dh_shlibdeps with the required arguments.
-	path_prepend=`mktemp -d /tmp/intercept.XXX`; \
+	path_prepend=`mktemp -d /tmp/intercept.XXXXXX`; \
 	echo "#$(SHELL)" > $${path_prepend}/dh_shlibdeps; \
 	echo "`which dh_shlibdeps` -- \
 	 -xlibuutil3linux -xlibnvpair3linux -xlibzfs4linux -xlibzpool4linux" \