Move swift-foundation-icu build after swift build

Author: jmschonfeld

utils/swift_build_support/swift_build_support/build_script_invocation.py

@@ -615,9 +615,6 @@ def compute_product_pipelines(self):
         builder.add_product(products.curl.LibCurl,
                             is_enabled=self.args.build_curl)
 
-        builder.add_product(products.foundation.SwiftFoundationICU,
-                            is_enabled=self.args.build_foundation)
-
         # Begin a build-script-impl pipeline for handling the compiler toolchain
         # and a subset of the tools that we build. We build these in this manner
         # to preserve current build-script-impl run behavior as we transition
@@ -637,6 +634,13 @@ def compute_product_pipelines(self):
         builder.add_impl_product(products.LibDispatch,
                                  is_enabled=self.args.build_libdispatch)
 
+        # Begin a pipeline to build Foundation's dependencies now that Swift
+        # has built. This needs to be done before Foundation can build
+        builder.begin_pipeline()
+
+        builder.add_product(products.foundation.SwiftFoundationICU,
+                            is_enabled=self.args.build_foundation)
+
         # Begin a new build-script-impl pipeline that builds libraries that we
         # build as part of build-script-impl but that we should eventually move
         # onto build-script products.