[gnome-directory-thumbnailer] build: Update autogen.sh from GNOME recommendation

[Philip Withnall <pwithnall src gnome org>]

commit 94d69d1013650b4e0836520014ef04eddb498a59
Author: Philip Withnall <philip tecnocode co uk>
Date:   Fri Mar 4 02:59:34 2016 +0000

    build: Update autogen.sh from GNOME recommendation
    
    https://wiki.gnome.org/Projects/GnomeCommon/Migration#autogen.sh
    
    This fixes a srcdir ≠ builddir issue.

 autogen.sh |   30 ++++++++++++++++--------------
 1 files changed, 16 insertions(+), 14 deletions(-)
---
diff --git a/autogen.sh b/autogen.sh
index 9748f35..8f27bec 100755
--- a/autogen.sh
+++ b/autogen.sh
@@ -1,35 +1,37 @@
 #!/bin/sh
 # Run this to generate all the initial makefiles, etc.
-srcdir=`dirname $0`
-test -z "$srcdir" && srcdir=.
+test -n "$srcdir" || srcdir=$(dirname "$0")
+test -n "$srcdir" || srcdir=.
 
-(test -f $srcdir/configure.ac) || {
-       echo "**Error**: Directory "\`$srcdir\'" does not look like the top-level project directory"
+olddir=$(pwd)
+
+cd $srcdir
+
+(test -f configure.ac) || {
+       echo "*** ERROR: Directory '$srcdir' does not look like the top-level project directory ***"
        exit 1
 }
 
-PKG_NAME=`autoconf --trace 'AC_INIT:$1' "$srcdir/configure.ac"`
+# shellcheck disable=SC2016
+PKG_NAME=$(autoconf --trace 'AC_INIT:$1' configure.ac)
 
 if [ "$#" = 0 -a "x$NOCONFIGURE" = "x" ]; then
-       echo "**Warning**: I am going to run \`configure' with no arguments." >&2
-       echo "If you wish to pass any to it, please specify them on the" >&2
-       echo \`$0\'" command line." >&2
+       echo "*** WARNING: I am going to run 'configure' with no arguments." >&2
+       echo "*** If you wish to pass any to it, please specify them on the" >&2
+       echo "*** '$0' command line." >&2
        echo "" >&2
 fi
 
-set -x
 aclocal --install || exit 1
 intltoolize --force --copy --automake || exit 1
-autoreconf --verbose --force --install -Wno-portability || exit 1
-set +x
+autoreconf --verbose --force --install || exit 1
 
+cd "$olddir"
 if [ "$NOCONFIGURE" = "" ]; then
-       set -x
        $srcdir/configure "$@" || exit 1
-       set +x
 
        if [ "$1" = "--help" ]; then exit 0 else
-               echo "Now type \`make\' to compile $PKG_NAME" || exit 1
+               echo "Now type 'make' to compile $PKG_NAME" || exit 1
        fi
 else
        echo "Skipping configure process."