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='2021-01-10 14:23:20 +0200'>2021-01-10</span></td><td><a href='/guix/commit/gnu/packages/patches/pulseview-qt515-compat.patch?id=d0fff8f840afc17be40bdc49bff52ed08d5a1a7b'>gnu: pulseview: Fix qt-5.15 compatibility.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/electronics.scm (pulseview)[source]: Add patch.
* gnu/packages/patches/pulseview-qt515-compat.patch: New file.
* gnu/local.mk (dist_patch_DATA): Register it.
</span></span></td><td>Efraim Flashner</td></tr>