remove -mt suffix from boost libraries built by depends

depends/packages/boost.mk

@@ -9,7 +9,7 @@ define $(package)_set_vars
 $(package)_config_opts_release=variant=release
 $(package)_config_opts_debug=variant=debug
 $(package)_config_opts=--layout=tagged --build-type=complete --user-config=user-config.jam
-$(package)_config_opts+=threading=multi link=static -sNO_BZIP2=1 -sNO_ZLIB=1
+$(package)_config_opts+=link=static -sNO_BZIP2=1 -sNO_ZLIB=1
 $(package)_config_opts_linux=threadapi=pthread runtime-link=shared
 $(package)_config_opts_darwin=--toolset=darwin-4.2.1 runtime-link=shared
 $(package)_config_opts_mingw32=binary-format=pe target-os=windows threadapi=win32 runtime-link=static