put back prebuilts, broken because of patches

mob.ini

@@ -15,8 +15,8 @@ nuget   = nuget.exe
 vswhere = vswhere.exe
 vcvars  =
 
-#[prebuilt]
-#boost   = false
+[prebuilt]
+boost   = true
 
 [versions]
 vs           = 16
@@ -25,7 +25,7 @@ vs_toolset   = 14.2
 sdk          = 10.0.18362.0
 sevenzip     = 19.00
 zlib         = 1.2.11
-boost        = 1.72.0-b1-rc1
+boost        = 1.73.0
 boost_vs     = 14.2
 python       = v3.8.1
 fmt          = 6.1.2

src/conf.cpp

@@ -44,7 +44,7 @@ static path_map g_tools =
 
 static bool_map g_prebuilt =
 {
-	//{"boost",   false}
+	{"boost",   false}
 };
 
 static string_map g_versions =

src/conf.h

@@ -54,7 +54,7 @@ struct prebuilt
 {
 	static bool by_name(const std::string& s);
 
-	//VALUE(boost);
+	VALUE(boost);
 };
 
 struct versions

src/tasks/boost.cpp

@@ -29,17 +29,17 @@ fs::path boost::root_lib_path(arch a)
 
 void boost::do_fetch()
 {
-	//if (prebuilt::boost())
-	//	fetch_prebuilt();
-	//else
+	if (prebuilt::boost())
+		fetch_prebuilt();
+	else
 		fetch_from_source();
 }
 
 void boost::do_build_and_install()
 {
-	//if (prebuilt::boost())
-	//	build_and_install_prebuilt();
-	//else
+	if (prebuilt::boost())
+		build_and_install_prebuilt();
+	else
 		build_and_install_from_source();
 }
 
@@ -55,6 +55,8 @@ void boost::do_clean_for_rebuild()
 
 void boost::fetch_prebuilt()
 {
+	cx().trace(context::generic, "using prebuilt boost");
+
 	const auto file = run_tool(downloader(prebuilt_url()));
 
 	run_tool(extractor()