bazel/macos: use MachineApple.cc on MacOS

On MacOS the MachineApple.cc must be used instead of
MachineLinux.cc. I added a select statement.

Signed-off-by: Friedrich Beckmann <friedrich.beckmann@tha.de>

BUILD

@@ -390,7 +390,10 @@ cc_library(
         "util",
         "verilog",
     ],
-    textual_hdrs = ["util/MachineLinux.cc"],
+    textual_hdrs = select({
+        "@platforms//os:osx": ["util/MachineApple.cc"],
+        "//conditions:default": ["util/MachineLinux.cc"],
+    }),
     visibility = ["//:__subpackages__"],
     deps = [
         "@cudd",