Avoid GNUism '\|' by using extended REs.

Index: gnetlist-legacy/tests/run-test
--- gnetlist-legacy/tests/run-test.orig
+++ gnetlist-legacy/tests/run-test
@@ -2,7 +2,7 @@
 
 ref="$1"
 tmp="`echo "x$1" | sed -e 's:.*/tests/::' -e 's:\\.out$::' -e 's:^x\\./::'`"
-stem="`echo "${tmp}" | sed -e 's:-spice-.*:@@@:' -e 's:\\(-[^-@]*\\|@@@\\)$::'`"
+stem="`echo "${tmp}" | sed -E -e 's:-spice-.*:@@@:' -e 's:(-[^-@]*|@@@)$::'`"
 backend="`echo "${tmp}" | sed -e "s:^${stem}-::"`"
 
 GNETLIST="${abs_top_builddir}/gnetlist-legacy/src/gnetlist-legacy"
