Create block special devices needed by test_BlockSpecial in GitLab CI jobs (!59)

From 23-Feb-2020 onwards, GNOME GitLab Continuous Integration test jobs
have been failing running unit tests which previously succeeded.  With
some extra debugging added into test_BlockSpecial to print 'bname' and
'bs' values in the failing tests, here are fragments from
tests/test-suite.log for the the test_BlockSpecial failures in a test CI
job:

    FAIL: test_BlockSpecial
    =======================
    ...
    [ RUN      ] BlockSpecialTest.NamedBlockSpecialObjectBlockDevice
    bname="/dev/sr0"
    bs=BlockSpecial{"/dev/sr0",0,0}
    test_BlockSpecial.cc:218: Failure
    Value of: bs.m_major > 0 || bs.m_minor > 0
      Actual: false
    Expected: true
    [  FAILED  ] BlockSpecialTest.NamedBlockSpecialObjectBlockDevice (0 ms)
    ...
    [ RUN      ] BlockSpecialTest.TwoNamedBlockSpecialObjectBlockDevices
    bname1="/dev/sr0"
    bname2="/dev/sda"
    bs1=BlockSpecial{"/dev/sr0",0,0}
    bs2=BlockSpecial{"/dev/sda",0,0}
    test_BlockSpecial.cc:250: Failure
    Value of: bs1.m_major != bs2.m_major || bs1.m_minor != bs2.m_minor
      Actual: false
    Expected: true
    [  FAILED  ] BlockSpecialTest.TwoNamedBlockSpecialObjectBlockDevices (1 ms)

Contents of /proc/partitions inside the Docker image when this test CI
job failed:

    $ cat /proc/partitions
    major minor  #blocks  name
      11        0    1048575 sr0
       8        0  573367448 sda
       8        1  573366407 sda1

And the listing of /dev/:

    $ ls -l /dev/
    total 0
    lrwxrwxrwx 1 root root   11 Mar  3 09:00 core -> /proc/kcore
    lrwxrwxrwx 1 root root   13 Mar  3 09:00 fd -> /proc/self/fd
    crw-rw-rw- 1 root root 1, 7 Mar  3 09:00 full
    drwxrwxrwt 2 root root   40 Mar  3 09:00 mqueue
    crw-rw-rw- 1 root root 1, 3 Mar  3 09:00 null
    lrwxrwxrwx 1 root root    8 Mar  3 09:00 ptmx -> pts/ptmx
    drwxr-xr-x 2 root root    0 Mar  3 09:00 pts
    crw-rw-rw- 1 root root 1, 8 Mar  3 09:00 random
    drwxrwxrwt 2 root root   40 Mar  3 09:00 shm
    lrwxrwxrwx 1 root root   15 Mar  3 09:00 stderr -> /proc/self/fd/2
    lrwxrwxrwx 1 root root   15 Mar  3 09:00 stdin -> /proc/self/fd/0
    lrwxrwxrwx 1 root root   15 Mar  3 09:00 stdout -> /proc/self/fd/1
    crw-rw-rw- 1 root root 5, 0 Mar  3 09:00 tty
    crw-rw-rw- 1 root root 1, 9 Mar  3 09:00 urandom
    crw-rw-rw- 1 root root 1, 5 Mar  3 09:00 zero

See how the test_BlockSpecial fixtures are getting major=0 and minor=0
for the block special devices they are testing with.  This is happening
because there aren't any entries in /dev for those disks and partitions
listed in /proc/partitions.  Assume that Docker in GNOME GitLab has
changed and that unneeded and unwanted devices in /dev are no longer
being created inside images.

In the test CI jobs execute new script, tests/makedev.sh, to create just
the first two block special devices mentioned in /proc/partitions needed
by test_BlockSpecial.

Closes !59 - Fix GNOME GitLab CI test job failures because of missing
             /dev entries

.gitlab-ci.yml

@@ -60,6 +60,8 @@ stages:
     - make -j $nproc
     # Exclude specific unit test which fails without /dev/disk in Docker images.
     - export GTEST_FILTER='-BlockSpecialTest.NamedBlockSpecialObjectBySymlinkMatches'
+    # Create needed /dev entries for unit tests in Docker images.
+    - tests/makedev.sh
     - make check
     - make distcheck
   # Save all files on job failure for investigation.

tests/makedev.sh

@@ -0,0 +1,24 @@
+#!/bin/sh
+#    Name: tests/makedev.sh
+# Purpose: Create /dev special files needed for GParted unit testing
+#          inside GitLab Docker CI images.
+#
+# Copyright (C) 2020 Mike Fleetwood
+#
+#  Copying and distribution of this file, with or without modification,
+#  are permitted in any medium without royalty provided the copyright
+#  notice and this notice are preserved.  This file is offered as-is,
+#  without any warranty.
+
+
+# Create first two block special devices named in /proc/partitions, if
+# they don't already exist, for test_BlockSpecial.
+awk '$1=="major" {next} NF==4 {printf "/dev/%s %s %s\n", $4, $1, $2; p++} p>=2 {exit}' /proc/partitions | \
+while read name maj min
+do
+	if test ! -e "$name"; then
+		echo mknod -m 0660 "$name" b $maj $min
+		mknod -m 0660 "$name" b $maj $min
+		chown root:disk "$name"
+	fi
+done