[Tests][SwiftPM] Tweak build script slightly.

We still need a small tweak to `swiftpm.py`.

Author: al45tair

utils/swift_build_support/swift_build_support/products/swiftpm.py

@@ -24,7 +24,7 @@
 from . import swift_testing
 from . import xctest
 from .. import shell
-from ..targets import StdlibDeploymentTarget
+from ..targets import StdlibDeploymentTarget, darwin_toolchain_prefix
 
 
 class SwiftPM(product.Product):
@@ -192,6 +192,6 @@ def _get_toolchain_path(host_target, product, args):
     if platform.system() == 'Darwin':
         # The prefix is an absolute path, so concatenate without os.path.
         toolchain_path += \
-            targets.darwin_toolchain_prefix(args.install_prefix)
+            darwin_toolchain_prefix(args.install_prefix)
 
     return toolchain_path