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 class='sub'>Wojtek's customized Guix</td><td class='sub right'></td></tr></table>
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<div class='path'>path: <a href='/guix/log/?id=c5e436b0b1a4d2d8637f8f08e662619f3f7fe881'>root</a>/<a href='/guix/log/gnu?id=c5e436b0b1a4d2d8637f8f08e662619f3f7fe881'>gnu</a>/<a href='/guix/log/gnu/packages?id=c5e436b0b1a4d2d8637f8f08e662619f3f7fe881'>packages</a>/<a href='/guix/log/gnu/packages/gkrellm.scm?id=c5e436b0b1a4d2d8637f8f08e662619f3f7fe881'>gkrellm.scm</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/gnu/packages/gkrellm.scm?id=c5e436b0b1a4d2d8637f8f08e662619f3f7fe881&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2021-12-13 17:48:25 +0100'>2021-12-13</span></td><td><a href='/guix/commit/gnu/packages/gkrellm.scm?id=8394619baceb118df92e355377fd543bb1aa501a'>gnu: Simplify package inputs.</a><span class='msg-avail'>...<span class='msg-tooltip'>This commit was obtained by running:

  ./pre-inst-env guix style

without any additional argument.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-03-07 01:41:23 +0100'>2020-03-07</span></td><td><a href='/guix/commit/gnu/packages/gkrellm.scm?id=64df1416c297af8ddff051bdbe3f2c001c5b8e1e'>gnu: gkrellm: Update to 2.3.11.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/gkrellm.scm (gkrellm): Update to 2.3.11.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>