depends: boost: Remove unnecessary _archiver_

We already have $(package)_ar, so just use that instead

Author: dongcarl

depends/packages/boost.mk

@@ -22,15 +22,14 @@ $(package)_toolset_$(host_os)=clang
 else
 $(package)_toolset_$(host_os)=gcc
 endif
-$(package)_archiver_$(host_os)=$($(package)_ar)
 $(package)_config_libraries=filesystem,system,thread,test
 $(package)_cxxflags=-std=c++11 -fvisibility=hidden
 $(package)_cxxflags_linux=-fPIC
 $(package)_cxxflags_android=-fPIC
 endef
 
 define $(package)_preprocess_cmds
-  echo "using $($(package)_toolset_$(host_os)) : : $($(package)_cxx) : <cxxflags>\"$($(package)_cxxflags) $($(package)_cppflags)\" <linkflags>\"$($(package)_ldflags)\" <archiver>\"$($(package)_archiver_$(host_os))\" <striper>\"$(host_STRIP)\"  <ranlib>\"$(host_RANLIB)\" <rc>\"$(host_WINDRES)\" : ;" > user-config.jam
+  echo "using $($(package)_toolset_$(host_os)) : : $($(package)_cxx) : <cxxflags>\"$($(package)_cxxflags) $($(package)_cppflags)\" <linkflags>\"$($(package)_ldflags)\" <archiver>\"$($(package)_ar)\" <striper>\"$(host_STRIP)\"  <ranlib>\"$(host_RANLIB)\" <rc>\"$(host_WINDRES)\" : ;" > user-config.jam
 endef
 
 define $(package)_config_cmds