/usr/bin/gdlib-config is in libgd-dev 2.1.0-3ubuntu0.11.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 | #!/bin/sh
#
# Return information about the local GD library installation
#
# Modified to use pkgconfig
pkg=gdlib
usage()
{
	cat <<EOF
Print information on GD library's version, configuration, and use.
Usage: gdlib-config [options]
Options:
	--libdir          # directory where GD library is installed
	--includedir      # directory where GD library headers are installed
	--version         # complete GD library version string
	--majorversion    # GD library major version number
	--minorversion    # GD library minor version number
	--revision        # GD library revision version number
	--ldflags         # options required for linking against GD library
	--libs            # libs required for linking against GD library
	--cflags          # options required for compiling GD library apps
	--includes        # same as --cflags
	--features        # lists features compiled into gd, separated by spaces.
                          # Currently (as of 2.1.1-dev) the optional features
                          # are GD_PNG, GD_JPEG, GD_XPM, GD_FREETYPE, and 
                          # GD_FONTCONFIG. When these features are reported by
                          # --features, it is safe to include calls to the
                          # related functions in your code.
	--all             # print a summary of all GD library configure options
EOF
	exit $1
}
if test $# -eq 0; then
	usage 1 1>&2
fi
while test $# -gt 0; do
    case "$1" in
    -*=*) optarg=`echo "$1" | sed 's/[-_a-zA-Z0-9]*=//'` ;;
    *) optarg= ;;
    esac
    case $1 in
    --libdir)
	pkg-config --variable=libdir ${pkg}
	;;
    --includedir)
	pkg-config --variable=includedir ${pkg}
	;;
    --version)
	pkg-config --modversion ${pkg}
	;;
    --majorversion)
	pkg-config --modversion ${pkg} | cut -f 1 -d .
	;;
    --minorversion)
	pkg-config --modversion ${pkg} | cut -f 2 -d .
	;;
    --revision)
	pkg-config --modversion ${pkg} | cut -f 3 -d .
	;;
    --ldflags)
	pkg-config --libs-only-L ${pkg}
	;;
    --libs)
	pkg-config --libs ${pkg}
	;;
    --cflags|--includes)
	pkg-config --cflags ${pkg}
	;;
    --features)
	echo GD_TIFF GD_VPX GD_XPM GD_JPEG GD_FONTCONFIG GD_FREETYPE GD_PNG GD_GIF GD_GIFANIM GD_OPENPOLYGON
	;;
    --all)
	echo "GD library  $($0 --version)@"
	echo "includedir: $($0 --includedir)"
	echo "cflags:     $($0 --cflags)"
	echo "ldflags:    $($0 --ldflags)"
	echo "libs:       $($0 --libs)"
	echo "libdir:     $($0 --libdir)"
	echo "features:   $($0 --features)"
	;;
    *)
	usage 1 1>&2
	;;
    esac
    shift
done
 |