stdlib: adjust the shims for MSVC mode compilation

The SwiftStdint.h header is used in the compiler as well.  The compiler may be
built with cl (Visual Studio) on Windows, which does not define
`__INTPTR_TYPE__` nor does it define `__INTPTR_WIDTH__`.  Simply define the
`__swift_{,u}intptr_t` typedefs as Microsoft does on that platform when building
with Visual Studio.

Author: compnerd

stdlib/public/SwiftShims/RefCount.h

@@ -1406,11 +1406,20 @@ typedef swift::InlineRefCounts InlineRefCounts;
 #endif
 
 // These assertions apply to both the C and the C++ declarations.
+#if defined(_MSC_VER) && !defined(__clang__)
+static_assert(sizeof(InlineRefCounts) == sizeof(InlineRefCountsPlaceholder),
+              "InlineRefCounts and InlineRefCountsPlaceholder must match");
+static_assert(sizeof(InlineRefCounts) == sizeof(__swift_uintptr_t),
+              "InlineRefCounts must be pointer-sized");
+static_assert(__alignof(InlineRefCounts) == __alignof(__swift_uintptr_t),
+              "InlineRefCounts must be pointer-aligned");
+#else
 _Static_assert(sizeof(InlineRefCounts) == sizeof(InlineRefCountsPlaceholder),
   "InlineRefCounts and InlineRefCountsPlaceholder must match");
 _Static_assert(sizeof(InlineRefCounts) == sizeof(__swift_uintptr_t),
   "InlineRefCounts must be pointer-sized");
 _Static_assert(_Alignof(InlineRefCounts) == _Alignof(__swift_uintptr_t),
   "InlineRefCounts must be pointer-aligned");
+#endif
 
 #endif

stdlib/public/SwiftShims/SwiftStdint.h

@@ -70,8 +70,20 @@ typedef unsigned __INT8_TYPE__ __swift_uint8_t;
 #define __swift_intn_t(n) __swift_join3(__swift_int, n, _t)
 #define __swift_uintn_t(n) __swift_join3(__swift_uint, n, _t)
 
+#if defined(_MSC_VER) && !defined(__clang__)
+#if defined(_WIN32)
+typedef __swift_int32_t __swift_intptr_t;
+typedef __swift_uint32_t __swift_uintptr_t;
+#elif defined(_WIN64)
+typedef __swift_int64_t __swift_intptr_t;
+typedef __swift_uint64_t __swift_uintptr_t;
+#else
+#error unknown windows pointer width
+#endif
+#else
 typedef __swift_intn_t(__INTPTR_WIDTH__) __swift_intptr_t;
 typedef __swift_uintn_t(__INTPTR_WIDTH__) __swift_uintptr_t;
 #endif
+#endif
 
 #endif // SWIFT_STDLIB_SHIMS_SWIFT_STDINT_H