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

Zcash: This also reverts b6d0996 which
fixes a PIE linking error, but likely breaks FreeBSD build support.

depends/packages/boost.mk

@@ -11,7 +11,7 @@ endif
 define $(package)_set_vars
 $(package)_config_opts_release=variant=release
 $(package)_config_opts_debug=variant=debug
-$(package)_config_opts=--layout=system
+$(package)_config_opts=--layout=system --user-config=user-config.jam
 $(package)_config_opts+=threading=multi link=static -sNO_BZIP2=1 -sNO_ZLIB=1
 $(package)_config_opts_linux=threadapi=pthread runtime-link=shared
 $(package)_config_opts_freebsd=cxxflags=-fPIC
@@ -36,9 +36,12 @@ endif
 
 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
+endef
+
 define $(package)_config_cmds
-  ./bootstrap.sh --without-icu --with-libraries=$($(package)_config_libraries) && \
-  sed -i -e "s|using gcc ;|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)\" : ;|" project-config.jam
+  ./bootstrap.sh --without-icu --with-libraries=$($(package)_config_libraries) --with-toolset=$($(package)_toolset_$(host_os))
 endef
 
 define $(package)_build_cmds