softethervpn: fix build on macos

host-compile fails on macos due to several reasons:
1. host-compile Makefile always selected for linux
2. macos host cc (clang) fails due to implicit-function-declaration
3. ar and ranlib tools are hardcoded in softethervpn Makefiles

All three issues are fixed by this patch

Signed-off-by: Sergey V. Lobanov <sergey@lobanov.in>

net/softethervpn/Makefile

@@ -11,7 +11,7 @@ include $(TOPDIR)/rules.mk
 PKG_NAME:=softethervpn
 PKG_VERSION:=4.38-9760
 PKG_VERREL:=rtm
-PKG_RELEASE:=1
+PKG_RELEASE:=2
 
 PKG_SOURCE:=softether-src-v$(PKG_VERSION)-$(PKG_VERREL).tar.gz
 PKG_SOURCE_URL:=https://github.com/SoftEtherVPN/SoftEtherVPN_Stable/releases/download/v$(PKG_VERSION)-$(PKG_VERREL)
@@ -37,13 +37,16 @@ include $(INCLUDE_DIR)/host-build.mk
 HOST_MAKE_FLAGS += -C $(HOST_BUILD_DIR)
 
 # Select 32 or 64 bit Makefile for host build depending on host architecture
-HOST_MAKE_FLAGS += -f src/makefiles/linux_$(if $(shell uname -m | grep 64),64,32)bit.mak
+HOST_MAKE_FLAGS += \
+	-f src/makefiles/$(if $(CONFIG_HOST_OS_MACOS),macos,linux)_$(if $(shell uname -m | grep 64),64,32)bit.mak
 
 HOST_LDFLAGS += -Wl,-rpath$(comma)$(STAGING_DIR_HOSTPKG)/lib
 # Prevent calling upstream configure
 define Host/Configure
 endef
 
+HOST_CFLAGS += $(if $(CONFIG_HOST_OS_MACOS),-Wno-implicit-function-declaration,)
+
 define Host/Compile
 	# Build hamcorebuilder using host compiler and let it generate
 	# the hamcore.se2 archive file