Merge pull request #10399 from github/redsun82/swift-macos-arm

Swift: print a helpful message on macOS ARM

Author: AlexDenisov

swift/rules.bzl

@@ -5,11 +5,7 @@ def _wrap_cc(rule, kwargs):
     _add_args(kwargs, "copts", [
         # Required by LLVM/Swift
         "-fno-rtti",
-    ] + select({
-        # temporary, before we do universal merging and have an arm prebuilt package, we make arm build x86
-        "@platforms//os:macos": ["-arch=x86_64"],
-        "//conditions:default": [],
-    }))
+    ])
     _add_args(kwargs, "features", [
         # temporary, before we do universal merging
         "-universal_binaries",

swift/tools/prebuilt/BUILD.bazel

@@ -1,21 +1,18 @@
 package(default_visibility = ["//swift:__subpackages__"])
 
 #TODO we will be introducing universal binaries at a later stage, when we have both architectures prebuilt for macOS
-# for the moment, we make arm build an x86_64 binary
-_arch_override = {
-    "darwin_arm64": "darwin_x86_64",
-}
-
+# for the moment, we require --cpu=darwin_x86_64 on an ARM macOS
 [
     alias(
         name = name,
-        actual = select({
-            "@bazel_tools//src/conditions:%s" % arch: "@swift_prebuilt_%s//:%s" % (
-                _arch_override.get(arch, arch),
-                name,
-            )
-            for arch in ("linux", "darwin_x86_64", "darwin_arm64")
-        }),
+        actual = select(
+            {
+                "@bazel_tools//src/conditions:%s" % arch: "@swift_prebuilt_%s//:%s" % (arch, name)
+                for arch in ("linux", "darwin_x86_64")
+            },
+            no_match_error = "Unsupported platform. Support for the ARM macOS platform is still a todo, " +
+                             "please pass --cpu=darwin_x86_64 for the time being",
+        ),
     )
     for name in ("swift-llvm-support", "swift-test-sdk")
 ]