JavaScript Backend: fix "improper shell usage errors" in testsuite

Description

The JS backend produces a lot of failures in the testsuite that look like:

Wrong exit code for T10955dyn()(expected 0 , actual 2 )
Stderr ( T10955dyn ):
--- /dev/null	2022-10-10 09:23:06.946692095 +0200
+++ "/tmp/ghctest-64akgqpm/test   spaces/testsuite/tests/haddock/perf/haddock_parser_perf.run/haddock_parser_perf.run.stderr.normalised"	2022-10-11 21:43:49.522168985 +0200
@@ -0,0 +1,2 @@
+egrep: warning: egrep is obsolescent; using grep -E
+egrep: warning: egrep is obsolescent; using grep -E
--- /dev/null	2022-10-10 09:23:06.946692095 +0200
+++ "/tmp/ghctest-64akgqpm/test   spaces/testsuite/tests/haddock/perf/haddock_renamer_perf.run/haddock_renamer_perf.run.stderr.normalised"	2022-10-11 21:43:49.885502306 +0200
@@ -0,0 +1,2 @@
+egrep: warning: egrep is obsolescent; using grep -E
+egrep: warning: egrep is obsolescent; using grep -E

Should be an easy fix.

Impacted Tests

• cabal01
• cabal03
• cabal04
• cabal05
• cabal06
• cabal08
• cabal09
• cabal10
• bkpcabal01
• bkpcabal02
• bkpcabal03
• bkpcabal04
• bkpcabal05
• bkpcabal06
• bkpcabal07