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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<tr><td><span title='2020-11-23 05:44:11 +0100'>2020-11-23</span></td><td><a href='/guix/commit/gnu/packages/lsof.scm?id=f942c09b663c3a48a1ae22ae96b69aabc323fd31'>gnu: lsof: Cross-compile.</a><span class='msg-avail'>...</span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2020-11-23 05:44:10 +0100'>2020-11-23</span></td><td><a href='/guix/commit/gnu/packages/lsof.scm?id=2bf502138c9c8cad945866061772fe0e1f4b7175'>gnu: lsof: Make test failures fatal.</a><span class='msg-avail'>...</span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2020-11-23 05:44:10 +0100'>2020-11-23</span></td><td><a href='/guix/commit/gnu/packages/lsof.scm?id=70303d073a4f9e9d9fdfa309c6fc350e80b63a60'>gnu: lsof: Respect #:tests?.</a><span class='msg-avail'>...</span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2020-11-23 05:44:10 +0100'>2020-11-23</span></td><td><a href='/guix/commit/gnu/packages/lsof.scm?id=518b21e058f9ccf23257a2afe1bbace280c5fe1d'>gnu: lsof: Update to 4.94.0.</a><span class='msg-avail'>...</span></td><td>Tobias Geerinckx-Rice</td></tr>