[ModuleInterface] Don't alias the stdlib or builtin module

Not aliasing the stdlib should allows it to be used in inlinable code.
Since builtin isn't imported explicitly, references to it shouldn't use
the alias.

rdar://104582241

Author: xymus

lib/Frontend/ModuleInterfaceSupport.cpp

@@ -81,6 +81,12 @@ static void printToolVersionAndFlagsComment(raw_ostream &out,
 
     for (ImportedModule import: imports) {
       StringRef importedName = import.importedModule->getNameStr();
+      // Skip Swift as it's commonly used in inlinable code,
+      // and Builtin as it's imported implicitly by name.
+      if (importedName == STDLIB_NAME ||
+          importedName == BUILTIN_NAME)
+        continue;
+
       if (AliasModuleNamesTargets.insert(importedName).second) {
         out << " -module-alias " << MODULE_DISAMBIGUATING_PREFIX <<
                importedName << "=" << importedName;

test/ModuleInterface/ambiguous-aliases-workaround-swiftinterface.swift

@@ -19,7 +19,7 @@
 // RUN:     -emit-module-interface-path %t/Client.swiftinterface \
 // RUN:     -emit-private-module-interface-path %t/Client.private.swiftinterface \
 // RUN:     %t/Client.swift -I %t -experimental-spi-only-imports \
-// RUN:     -alias-module-names-in-module-interface
+// RUN:     -alias-module-names-in-module-interface -parse-stdlib
 // RUN: %target-swift-typecheck-module-from-interface(%t/Client.swiftinterface) -I%t
 // RUN: %target-swift-typecheck-module-from-interface(%t/Client.private.swiftinterface) -module-name Client -I%t
 
@@ -48,3 +48,10 @@ import PublicLib
 // PUBLIC: import Module___PublicLib
 // PRIVATE: import Module___PublicLib
 // PRIVATE: import Module___SPILib
+
+public func builtinUser(_ a: Builtin.Int32) {}
+
+@inlinable
+public func builtinInlinableUser() {
+    var a: Builtin.Int32
+}

test/ModuleInterface/ambiguous-aliases-workaround.swift

@@ -77,6 +77,7 @@ public struct SomeType {
     @inlinable
     public func inlinableFunc() {
         var x: AmbiguousClientName
+        var y: Swift.Int
     }
 }