Characters displayed as unfilled rectangles in a relocated gtk+-2.0 build

[cph <cph chi-square-works com>]

Hi,

I collected all the necessary packages[*] to build the latest 
gtk+-2.24.30.  As I would like to create my own gtk+-2.0 
runtime environment, I configured all these packages with 
--prefix=/tmp/g2 before I ran "make" on them.  Next, without 
deleting a single bit in /tmp/g2, I compiled my program with 
the new stuff in /tmp/g2.  The resulting executable ran fine.  

To further test if I could make a runtime environment out of
the stuff in /tmp/g2, I renamed /tmp/g2 as /tmp/g22 and set
environment variables LD_LIBRARY_PATH and GTK_EXE_PREFIX
to /tmp/g22/lib and /tmp/g22, respectively.  Upon invoking
my executable, I got this message:
  Fontconfig error: Cannot load default config file
and all characters in the windows popped up by my executable
were replaced by unfilled rectangles.  After I set the
environment variable FONTCONFIG_PATH to /tmp/g22/etc/fonts
and ran my executable again, I did not get the "Fontconfig
error: Cannot load ..." error message but all characters
were still displayed as unfilled rectangles.  I also noticed
that fontconfig recreated the /tmp/g2/var/cache/fontconfig/
directory, into which it deposited a CACHEDIR.TAG file and
a bunch of *.cache-7 files.

I'll be grateful if someones could shed any light on how to
fix this problem.

Best wishes,

-cph

PS: The packages were:
      glib-2.28.8
      pixman-0.34.0
      fontconfig-2.11.95
      freetype-2.6
      cairo-1.14.6
      gobject-introspection-0.10.8
      atk-1.30.0
      gdk-pixbuf-2.21.7
      pango-1.28.4
      gtk+-2.24.30
      gtk-engines-2.20.2

PPS: This was on a Ubuntu Mate 14.04.2 32-bit virtual machine.