shims: invert the condition and prefer the clang path

Because the shims are generally meant for the standard library build,
which requires clang, we can default to using the compiler vended
information for the types.

Author: compnerd

stdlib/public/SwiftShims/SwiftStddef.h

@@ -17,15 +17,22 @@
 // result, using stddef.h here would pull in Darwin module (which includes
 // libc). This creates a dependency cycle, so we can't use stddef.h in
 // SwiftShims.
+//
 // On Linux, the story is different. We get the error message
 // "/usr/include/x86_64-linux-gnu/sys/types.h:146:10: error: 'stddef.h' file not
 // found"
 // This is a known Clang/Ubuntu bug.
-#if !defined(__APPLE__) && !defined(__linux__)
+//
+// On Windows, the complicated setup between clang and MSVC causes a cicular
+// dependency between `ucrt` and `SwiftShims`, preventing a successful build of
+// the module.
+//
+// Opt to use teh compiler vended type whenever possible.
+#if defined(__clang__)
+typedef __SIZE_TYPE__ __swift_size_t;
+#else
 #include <stddef.h>
 typedef size_t __swift_size_t;
-#else
-typedef __SIZE_TYPE__ __swift_size_t;
 #endif
 
 // This selects the signed equivalent of the unsigned type chosen for size_t.

test/Serialization/autolinking-inlinable-inferred.swift

@@ -55,13 +55,11 @@ bfunc()
 // CHECK-NORMAL-SAME: [[PUBLIC:![0-9]+]],
 // CHECK-NORMAL-SAME: [[SWIFTONONESUPPORT:![0-9]+]],
 // CHECK-NORMAL-SAME: [[SWIFTCORE:![0-9]+]],
-// CHECK-NORMAL-windows-msvc-SAME: [[STDIO:![0-9]+]],
 
 // This is the same set as the above, just in a different order due to a
 // different traversal of the transitive import graph.
 // CHECK-IMPL_ONLY-SAME: [[SWIFTONONESUPPORT:![0-9]+]],
 // CHECK-IMPL_ONLY-SAME: [[SWIFTCORE:![0-9]+]],
-// CHECK-IMPL_ONLY-windows-msvc-SAME: [[STDIO:![0-9]+]],
 // CHECK-IMPL_ONLY-SAME: [[MODULE:![0-9]+]],
 // CHECK-IMPL_ONLY-SAME: [[PUBLIC:![0-9]+]],
 
@@ -77,7 +75,6 @@ bfunc()
 // CHECK-DAG: [[PUBLIC]] = !{!{{"-lautolinking_public"|"/DEFAULTLIB:autolinking_public.lib"}}}
 // CHECK-DAG: [[SWIFTONONESUPPORT]] = !{!{{"-lswiftSwiftOnoneSupport"|"/DEFAULTLIB:swiftSwiftOnoneSupport.lib"}}}
 // CHECK-DAG: [[SWIFTCORE]] = !{!{{"-lswiftCore"|"/DEFAULTLIB:swiftCore.lib"}}}
-// CHECK-windows-msvc-DAG: [[STDIO]] = !{!"/DEFAULTLIB:legacy_stdio_definitions.lib"}
 // CHECK-DAG: [[OTHER]] = !{!{{"-lautolinking_other"|"/DEFAULTLIB:autolinking_other.lib"}}}
 // CHECK-DAG: [[OTHER2]] = !{!{{"-lautolinking_other2"|"/DEFAULTLIB:autolinking_other2.lib"}}}
 // CHECK-DAG: [[OBJC]] = !{!{{"-lobjc"|"/DEFAULTLIB:objc.lib"}}}