component/coreutils: add version 9.1 which is needed for gitlab-backup

Split command which is used to split pgdump files before push to gitlab backup repository crash during
backup process. This problem occurs with version starting from 9.2, older versions doesn't have this problem.
The version 9.1 is used for gitlab-backup so.

For more details, see: !1503 (diffs, comment 197515)

component/coreutils/buildout.cfg

@@ -19,6 +19,13 @@ environment =
   PATH=${perl:location}/bin:${xz-utils:location}/bin:%(PATH)s
   LDFLAGS=-Wl,--as-needed -L${gmp:location}/lib -Wl,-rpath=${gmp:location}/lib
 
+# Latest version of command split in coreutils is not working in gitlab backup
+# For more details, see: https://lab.nexedi.com/nexedi/slapos/merge_requests/1503/diffs#note_197515
+[coreutils-9.1]
+<= coreutils
+url = https://ftp.gnu.org/gnu/coreutils/coreutils-9.1.tar.xz
+md5sum = 8b1ca4e018a7dce9bb937faec6618671
+
 [coreutils-output]
 # Shared binary location to ease migration
 recipe = plone.recipe.command