libdpkg: Set umask to the expected value of 0022 in tar test case

There's no guarantee the build system will have the same umask as any
other system. Make sure to set it to what we expect.

debian/changelog

@@ -2,6 +2,8 @@ dpkg (1.17.15) UNRELEASED; urgency=low
 
   * Do not blacklist pie and stackprotector build flags on mips/mipsel.
     Thanks to Aurelien Jarno <aurelien@aurel32.net>. Closes: #763672
+  * Fix build failures due to mismatched umask in libdpkg tar test case.
+    Set it to a known value of 0022.
 
  -- Guillem Jover <guillem@debian.org>  Mon, 06 Oct 2014 02:43:41 +0200
 

lib/dpkg/test/t-tar.t

@@ -32,6 +32,9 @@ my $srcdir = $ENV{srcdir} || '.';
 my $builddir = $ENV{builddir} || '.';
 my $tmpdir = 't.tmp/t-tar';
 
+# Set a known umask.
+umask 0022;
+
 sub create {
     my ($pathname) = @_;