Add commented out workaround for #571240

jhbuildrc-gnome-shell: Remove obsolete setting of
   os.environ['INSTALL'] - setting installprog is the modern way
   to do it.
jhbuildrc-custom-example: Show how to override installprog to
  work around #571240 on Arch Linux.

tools/build/jhbuildrc-custom-example

@@ -11,3 +11,8 @@
 # Directory where to install
 #
 #prefix = '/opt/gnome-shell/install'
+
+# Work around http://bugzilla.gnome.org/show_bug.cgi?id=571240 if
+# your 'install' program is somewhere other than /usr/bin/install
+# (affects: Arch Linux)
+#installprog = 'bin/install'

tools/build/jhbuildrc-gnome-shell

@@ -58,9 +58,6 @@ if _pkgconfig.returncode == 0:
     if os.path.exists(_libdir + '/libmozjs.so'):
         addpath('LD_LIBRARY_PATH', _libdir)
 
-# Rebuild faster
-os.environ['INSTALL'] = os.path.expanduser('~/bin/install-check')
-
 # Import optional user RC for further customization. You can override
 # the prefix or default build setup for example, or CFLAGS or
 # module_autogenargs, etc.