SILGen: Use public_external linkage for __dso_handle instead of hidden_external

This allows it to be referenced from inlinable functions.

Fixes <rdar://problem/32597278>.

Author: slavapestov

lib/SILGen/SILGenExpr.cpp

@@ -2927,7 +2927,7 @@ visitMagicIdentifierLiteralExpr(MagicIdentifierLiteralExpr *E, SGFContext C) {
     auto DSOGlobal = SGF.SGM.M.lookUpGlobalVariable("__dso_handle");
     if (!DSOGlobal)
       DSOGlobal = SILGlobalVariable::create(SGF.SGM.M,
-                                            SILLinkage::HiddenExternal,
+                                            SILLinkage::PublicExternal,
                                             IsNotSerialized, "__dso_handle",
                                             BuiltinRawPtrTy);
     auto DSOAddr = SGF.B.createGlobalAddr(SILLoc, DSOGlobal);

test/SILGen/dso_handle.swift

@@ -1,6 +1,6 @@
 // RUN: %target-swift-frontend -Xllvm -sil-full-demangle -emit-silgen %s | %FileCheck %s
 
-// CHECK: sil_global hidden_external [[DSO:@__dso_handle]] : $Builtin.RawPointer
+// CHECK: sil_global [[DSO:@__dso_handle]] : $Builtin.RawPointer
 
 // CHECK-LABEL: sil @main : $@convention(c)
 // CHECK: bb0
@@ -13,4 +13,12 @@ func printDSOHandle(dso: UnsafeRawPointer = #dsohandle) -> UnsafeRawPointer {
   return dso
 }
 
+@_inlineable public func printDSOHandleInlineable(dso: UnsafeRawPointer = #dsohandle) -> UnsafeRawPointer {
+  return dso
+}
+
+@_inlineable public func callsPrintDSOHandleInlineable() {
+  printDSOHandleInlineable()
+}
+
 _ = printDSOHandle()