regroup list of OSes for install inside common variable

within lib/install_oses.mk.

fixes #4445

lib/install_oses.mk

@@ -0,0 +1,17 @@
+# ################################################################
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under both the BSD-style license (found in the
+# LICENSE file in the root directory of this source tree) and the GPLv2 (found
+# in the COPYING file in the root directory of this source tree).
+# You may select, at your option, one of the above-listed licenses.
+# ################################################################
+
+# This included Makefile provides the following variables :
+# UNAME, INSTALL_OS_LIST
+
+UNAME := $(shell sh -c 'MSYSTEM="MSYS" uname')
+
+# List of OSes for which target install is supported
+INSTALL_OS_LIST ?= Linux Darwin GNU/kFreeBSD GNU OpenBSD FreeBSD NetBSD DragonFly SunOS Haiku AIX MSYS_NT% CYGWIN_NT%