Make t.smoke more robust. FreeBSD Bug#240914.

NEWS

@@ -71,6 +71,12 @@ fetchmail 6.4.2 (not yet released):
   inside the table, which is unsupported by FreeBSD 12's mandoc(1) formatter.
   FreeBSD Bug#241032, reported by Helge Oldach.
 
+## CHANGES:
+* Make t.smoke more robust and use temporary directory as FETCHMAILHOME, to make
+  sure that the home directory resolves for the user running the test suite
+  even if the environment isn't perfect. Reported by Konstantin Belousov,
+  analysed by Corey Halpin, FreeBSD Bug#240914.
+
 fetchmail 6.4.1 (released 2019-09-28, 27473 LoC):
 
 ## REGRESSION FIXES:

t.smoke

@@ -3,9 +3,20 @@
 # This is a rudimentary tests to see if fetchmail can parse a trivial
 # configuration and dump it in human-readable and machine-readable form.
 
-set -e
-trap 'rm -f t.rc.$$' 0
-cp "${srcdir}/t.rc" t.rc.$$
-chmod 0400 t.rc.$$
-./fetchmail -V -f t.rc.$$ >/dev/null
-./fetchmail --configdump -f t.rc.$$ >/dev/null
+set -eu
+: "${TMPDIR:=/tmp}"
+{
+	dir=`(umask 077 && mktemp -d "$TMPDIR/t.smoke.XXXXXX")` 2>/dev/null \
+		&& test -d "$dir"
+} || {
+	dir=$TMPDIR/t.smoke.$$-$RANDOM
+		(umask 077 && mkdir "$dir")
+}
+trap 'r=$? ; rm -fr t.rc.$$ $dir ; exit $r' 0
+cp "${srcdir}/t.rc" $dir/t.rc.$$
+chmod 0400 $dir/t.rc.$$
+HOME=$dir
+FETCHMAILHOME=$dir
+export HOME FETCHMAILHOME
+./fetchmail -V -f $dir/t.rc.$$ >/dev/null
+./fetchmail --configdump -f $dir/t.rc.$$ >/dev/null