Use regexes to handle 'cabal.exe' in integration test output

cabal-install/cabal-install.cabal

@@ -36,6 +36,8 @@ Extra-Source-Files:
   tests/IntegrationTests/custom/should_run/plain/Setup.hs
   tests/IntegrationTests/custom/should_run/plain/plain.cabal
   tests/IntegrationTests/exec/common.sh
+  tests/IntegrationTests/exec/should_fail/exit_with_failure_without_args.err
+  tests/IntegrationTests/exec/should_fail/exit_with_failure_without_args.sh
   tests/IntegrationTests/exec/should_run/Foo.hs
   tests/IntegrationTests/exec/should_run/My.hs
   tests/IntegrationTests/exec/should_run/adds_sandbox_bin_directory_to_path.out
@@ -46,7 +48,6 @@ Extra-Source-Files:
   tests/IntegrationTests/exec/should_run/can_run_executables_installed_in_sandbox.sh
   tests/IntegrationTests/exec/should_run/configures_cabal_to_use_sandbox.sh
   tests/IntegrationTests/exec/should_run/configures_ghc_to_use_sandbox.sh
-  tests/IntegrationTests/exec/should_run/exit_with_failure_without_args.sh
   tests/IntegrationTests/exec/should_run/my.cabal
   tests/IntegrationTests/exec/should_run/runs_given_command.out
   tests/IntegrationTests/exec/should_run/runs_given_command.sh

cabal-install/tests/IntegrationTests/exec/should_fail/exit_with_failure_without_args.err

+RE:^cabal(\.exe)?: Please specify an executable to run$

cabal-install/tests/IntegrationTests/exec/should_fail/exit_with_failure_without_args.sh

+. ../common.sh
+
+cabal exec

cabal-install/tests/IntegrationTests/exec/should_run/exit_with_failure_without_args.sh

-. ../common.sh
-
-# We should probably be using a .err file and should_fail,
-# but this fails on windows due to the ".exe" on the cabal
-# executable in the output.
-cabal exec 2>&1 > /dev/null | grep "Please specify an executable to run"

cabal-install/tests/IntegrationTests/user-config/should_fail/doesnt_overwrite_without_f.err

-cabal: ./cabal-config already exists.
+RE:^cabal(\.exe)?: \./cabal-config already exists\.$