[build-script] Add support for specifying that a product is a non-darwin only product.

We have a few of these like foundation, libdispatch, icu, xctest that are built
outside of build-script on Darwin.

Author: gottesmm

utils/swift_build_support/swift_build_support/products/foundation.py

@@ -46,3 +46,7 @@ def get_dependencies(cls):
                 swift.Swift,
                 lldb.LLDB,
                 libdispatch.LibDispatch]
+
+    @classmethod
+    def is_nondarwin_only_build_product(cls):
+        return True

utils/swift_build_support/swift_build_support/products/libdispatch.py

@@ -36,6 +36,10 @@ def product_source_name(cls):
         """
         return "swift-corelibs-libdispatch"
 
+    @classmethod
+    def is_nondarwin_only_build_product(cls):
+        return True
+
     @classmethod
     def get_dependencies(cls):
         return [cmark.CMark,

utils/swift_build_support/swift_build_support/products/libicu.py

@@ -33,6 +33,10 @@ def product_source_name(cls):
         """
         return "icu"
 
+    @classmethod
+    def is_nondarwin_only_build_product(cls):
+        return True
+
     @classmethod
     def get_dependencies(cls):
         return [cmark.CMark,

utils/swift_build_support/swift_build_support/products/product.py

@@ -66,6 +66,13 @@ def is_swiftpm_unified_build_product(cls):
         """
         return False
 
+    @classmethod
+    def is_nondarwin_only_build_product(cls):
+        """Returns true if this target should be skipped in darwin builds when
+        inferring dependencies.
+        """
+        return False
+
     @classmethod
     def get_dependencies(cls):
         """Return a list of products that this product depends upon"""

utils/swift_build_support/swift_build_support/products/xctest.py

@@ -48,3 +48,7 @@ def get_dependencies(cls):
                 lldb.LLDB,
                 libdispatch.LibDispatch,
                 foundation.Foundation]
+
+    @classmethod
+    def is_nondarwin_only_build_product(cls):
+        return True