Honor TMPDIR environment variable

Replace all mktemp(1) invocations that hardcode "/tmp" with `mktemp
--tmpdir` and change templates accordingly.

Note that "--tmpdir" is GNU-ish which is okay given that we currently
support Arch Linux only anyway.

Signed-off-by: Lukas Fleischer <archlinux@cryptocrack.de>

checkpkg.in

@@ -24,7 +24,7 @@ if [[ $arch == 'any' ]]; then
 fi
 
 STARTDIR=$(pwd)
-TEMPDIR=$(mktemp -d /tmp/checkpkg-script.XXXX)
+TEMPDIR=$(mktemp -d --tmpdir checkpkg-script.XXXX)
 cd "$TEMPDIR"
 
 for _pkgname in "${pkgname[@]}"; do

lddd.in

@@ -9,7 +9,7 @@ IFS="${IFS}:"
 libdirs="/lib /usr/lib /usr/local/lib $(cat /etc/ld.so.conf.d/*)"
 extras=
 
-TEMPDIR=$(mktemp -d /tmp/lddd-script.XXXX)
+TEMPDIR=$(mktemp -d --tmpdir lddd-script.XXXX)
 
 echo 'Go out and drink some tea, this will take a while :) ...'
 #  Check ELF binaries in the PATH and specified dir trees.