depends: boost: Specify toolset to bootstrap.sh

b2 will pickup our user-config.jam just fine, however, bootstrap.sh has
its own toolset autodetect mechanism, which doesn't GAF about our
user-config.jam

depends/packages/boost.mk

@@ -33,7 +33,7 @@ define $(package)_preprocess_cmds
 endef
 
 define $(package)_config_cmds
-  ./bootstrap.sh --without-icu --with-libraries=$($(package)_config_libraries)
+  ./bootstrap.sh --without-icu --with-libraries=$($(package)_config_libraries) --with-toolset=$($(package)_toolset_$(host_os))
 endef
 
 define $(package)_build_cmds