libreswan: fix build on macos

libreswan makefile detects macos (darwin) and changes build logic
but OpenWrt is always Linux so it is required to specify linux as
target platfrom

This patch specifies Linux as a target platfrom

Signed-off-by: Sergey V. Lobanov <sergey@lobanov.in>
(cherry picked from commit 270e8eabc3)

net/libreswan/Makefile

@@ -8,7 +8,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=libreswan
 PKG_VERSION:=4.6
-PKG_RELEASE:=1
+PKG_RELEASE:=2
 
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.gz
 PKG_SOURCE_URL:=https://download.libreswan.org/
@@ -85,6 +85,8 @@ MAKE_FLAGS+= \
     FINALRUNDIR="/var/run/pluto" \
     FINALNSSDIR="/etc/ipsec.d" \
     MODPROBEARGS="-q" \
+    OSDEP=linux \
+    BUILDENV=linux \
     ARCH="$(LINUX_KARCH)" \
 
 define Build/Prepare