build: export filtered -lz flag in config.mak

This is needed to link tools/cws2fws using a linker with non-standard
command line syntax.
Signed-off-by: Mans Rullgard <mans@mansr.com>

Makefile

@@ -93,7 +93,7 @@ all: $(PROGS)
 $(TOOLS): %$(EXESUF): %.o
 	$(LD) $(LDFLAGS) $(LD_O) $< $(ELIBS)
 
-tools/cws2fws$(EXESUF): ELIBS = -lz
+tools/cws2fws$(EXESUF): ELIBS = $(ZLIB)
 
 config.h: .config
 .config: $(wildcard $(FFLIBS:%=$(SRC_PATH)/lib%/all*.c))

configure

@@ -3561,6 +3561,7 @@ TARGET_EXEC=$target_exec
 TARGET_PATH=$target_path
 LIBS-avplay=$sdl_libs
 CFLAGS-avplay=$sdl_cflags
+ZLIB=$($ldflags_filter -lz)
 LIB_INSTALL_EXTRA_CMD=$LIB_INSTALL_EXTRA_CMD
 EXTRALIBS=$extralibs
 INSTALL=install