Bootstrap: Install dispatch in stage0

The concurrency runtimes require that dispatch is installed or it will
fail to load at launch. The C library is built as part of the
concurrency build but is not installed. We need to install a copy of
dispatch so that programs that link concurrency run.

(cherry picked from commit f36391d)

Author: etcwilde

utils/build-presets.ini

@@ -3127,6 +3127,7 @@ swift-include-tests=0
 llvm-include-tests=0
 
 release
+libdispatch
 
 skip-early-swiftsyntax
 skip-early-swift-driver
@@ -3159,6 +3160,7 @@ llvm-install-components=llvm-ar;llvm-ranlib;clang;clang-resource-headers;compile
 
 install-llvm
 install-swift
+install-libdispatch
 
 # Build Toolchain Requirements:
 # - C/C++ compiler