Install everything in PREFIX, set EXTRA_PATH to find it there.

--- ./Makefile.in~	2016-02-06 01:29:16.595090365 +0100
+++ ./Makefile.in	2016-02-06 09:29:04.286008931 +0100
@@ -133,9 +133,9 @@
 # require for testing here (like TCLX_LIBRARY).
 #========================================================================

-EXTRA_PATH	= $(top_builddir):$(TCL_BIN_DIR)
+EXTRA_PATH	= $(top_builddir):$(TCL_BIN_DIR):$(libdir)
 #EXTRA_PATH     = $(top_builddir):$(TCL_BIN_DIR):$(TK_BIN_DIR)
-TCLLIBPATH      = $(top_builddir)
+TCLLIBPATH      = $(pkglibdir)
 TCLSH_ENV	= TCL_LIBRARY=`@CYGPATH@ $(TCL_SRC_DIR)/library` \
 		  @LD_LIBRARY_PATH_VAR@="$(EXTRA_PATH):$(@LD_LIBRARY_PATH_VAR@)" \
 		  PATH="$(EXTRA_PATH):$(PATH)" \
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<div class='path'>path: <a href='/guix/log/?id=cd436bf05a8344acf4462f3602e7d360821a902a'>root</a>/<a href='/guix/log/doc?id=cd436bf05a8344acf4462f3602e7d360821a902a'>doc</a>/<a href='/guix/log/doc/images?id=cd436bf05a8344acf4462f3602e7d360821a902a'>images</a>/<a href='/guix/log/doc/images/coreutils-bag-graph.dot?id=cd436bf05a8344acf4462f3602e7d360821a902a'>coreutils-bag-graph.dot</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/doc/images/coreutils-bag-graph.dot?id=cd436bf05a8344acf4462f3602e7d360821a902a&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2015-10-15 23:11:29 +0200'>2015-10-15</span></td><td><a href='/guix/commit/doc/images/coreutils-bag-graph.dot?id=3d2a9c8c8e65ed12e8395e744d3759fa2dd2edb8'>doc: Regenerate 'guix graph' examples.</a><span class='msg-avail'>...<span class='msg-tooltip'>* doc/images/coreutils-bag-graph.dot, doc/images/coreutils-graph.dot:
  Regenerate from current packages.  This removes the weird dependency
  on 'sed'.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2015-08-27 00:49:23 +0200'>2015-08-27</span></td><td><a href='/guix/commit/doc/images/coreutils-bag-graph.dot?id=888569161c0cb55a2700806aded7128cfe605857'>Add 'guix graph'.</a><span class='msg-avail'>...<span class='msg-tooltip'>* guix/scripts/graph.scm, tests/graph.scm, tests/guix-graph.sh,
  doc/images/coreutils-bag-graph.dot, doc/images/coreutils-graph.dot: New
  files.
* Makefile.am (MODULES): Add guix/scripts/graph.scm.
  (SH_TESTS): Add tests/guix-graph.sh.
  (SCM_TESTS): Add tests/graph.scm.
* doc.am (DOT_FILES, DOT_VECTOR_GRAPHICS): New variables.
  (EXTRA_DIST): Use them.
  (dist_infoimage_DATA): Use $(DOT_FILES).
  (pdf-local, info-local, ps-local): Likewise.
* doc/guix.texi (Packages with Multiple Outputs): Add cross-reference to 'guix
  graph'.
  (Invoking guix gc): Likewise.
  (Invoking guix graph): New section.
</span></span></td><td>Ludovic Courtès</td></tr>