[Build] Skip early-* on non-darwin hosts

These builds do not work outside of darwin currently. Rather than adding
the skip to all the necessary build presets, just disable in the product
instead.

(cherry picked from commit 97a6f3b)

Author: bnbarham

utils/build-presets.ini

@@ -851,11 +851,6 @@ installable-package=%(installable_package)s
 # in Linux CI bots
 relocate-xdg-cache-home-under-build-subdir
 
-# Temporarily disable early swift driver/syntax builds so that linux images
-# can use the swift release images as a base.
-skip-early-swift-driver
-skip-early-swiftsyntax
-
 [preset: buildbot_linux_base]
 mixin-preset=
     mixin_linux_installation

utils/swift_build_support/swift_build_support/products/earlyswiftdriver.py

@@ -11,6 +11,7 @@
 # ----------------------------------------------------------------------------
 
 import os
+import sys
 
 from . import earlyswiftsyntax
 from . import product
@@ -42,6 +43,11 @@ def is_before_build_script_impl_product(cls):
         return True
 
     def should_build(self, host_target):
+        # Temporarily disable for non-darwin since this build never works
+        # outside of that case currently.
+        if sys.platform != 'darwin':
+            return False
+
         if self.is_cross_compile_target(host_target):
             return False
 

utils/swift_build_support/swift_build_support/products/earlyswiftsyntax.py

@@ -10,6 +10,8 @@
 #
 # ----------------------------------------------------------------------------
 
+import sys
+
 from . import cmake_product
 from .. import toolchain
 
@@ -32,6 +34,11 @@ def is_before_build_script_impl_product(cls):
         return True
 
     def should_build(self, host_target):
+        # Temporarily disable for non-darwin since this build never works
+        # outside of that case currently.
+        if sys.platform != 'darwin':
+            return False
+
         if self.args.build_early_swiftsyntax:
             if toolchain.host_toolchain().find_tool("swift") is None:
                 warn_msg = 'Host toolchain could not locate a '\