GNU grep 3.8 introduces some warnings on certain regexes
https://build.opensuse.org/request/show/1001097

> Regular expressions with stray backslashes now cause warnings

Seems to break libtool tests that check stderr (?)
https://build.opensuse.org/package/live_build_log/home:AndreasStieger:branches:Base:System/libtool:testsuite/localdep/x86_64

[ 1902s] ./link-order.at:106: if $EGREP relinking stderr; then
[ 1902s]          $EGREP " -L.*\/new\/lib -lb -L.*\/old\/lib -lcee" stdout
[ 1902s]        else :; fi
[ 1902s] --- /dev/null    2022-09-04 15:44:09.608000000 +0000
[ 1902s] +++
/home/abuild/rpmbuild/BUILD/libtool-2.4.7/tests/testsuite.dir/at-groups/66/stderr
   2022-09-04 15:50:25.548000000 +0000
[ 1902s] @@ -0,0 +1,4 @@
[ 1902s] +/usr/bin/grep: warning: stray \ before /
[ 1902s] +/usr/bin/grep: warning: stray \ before /
[ 1902s] +/usr/bin/grep: warning: stray \ before /
[ 1902s] +/usr/bin/grep: warning: stray \ before /
[ 1902s] stdout:
[ 1902s] libtool: warning: relinking 'src/liba.la'
[ 1902s] libtool: relink: gcc -shared  -fPIC -DPIC  src/.libs/a.o   -Wl,-rpath
-Wl,/home/abuild/rpmbuild/BUILD/libtool-2.4.7/tests/testsuite.dir/066/new/lib
-Wl,-rpath
-Wl,/home/abuild/rpmbuild/BUILD/libtool-2.4.7/tests/testsuite.dir/066/old/lib
-L/home/abuild/rpmbuild/BUILD/libtool-2.4.7/tests/testsuite.dir/066/new/lib -lb
-L/home/abuild/rpmbuild/BUILD/libtool-2.4.7/tests/testsuite.dir/066/old/lib
-lcee  -O2 -fstack-protector-strong -g   -Wl,-soname -Wl,liba.so.0 -o
src/.libs/liba.so.0.0.0
[ 1902s] wrong link order
[ 1902s] 66. link-order.at:27: 66. Link order test (link-order.at:27): FAILED
(link-order.at:106)

Code in
https://github.com/autotools-mirror/libtool/blob/v2.4.7/tests/link-order.at#L106-L107