Frontend: re-serialise static library status

When compiling the swiftmodule from the textual swift interface, ensure
that we re-serialise the static or dynamic nature of the module. This is
required for proper code generation where the static and dynamic linking
is material to symbolic references. This also opens the possibility of
optimizations on other platforms via internalisation of the symbols.

Fixes: swiftlang#77756

Author: compnerd

lib/Frontend/ModuleInterfaceBuilder.cpp

@@ -279,6 +279,7 @@ std::error_code ExplicitModuleInterfaceBuilder::buildSwiftModuleFromInterface(
   // optimization pipeline.
   SerializationOptions SerializationOpts;
   std::string OutPathStr = OutputPath.str();
+  SerializationOpts.StaticLibrary = FEOpts.Static;
   SerializationOpts.OutputPath = OutPathStr.c_str();
   SerializationOpts.ModuleLinkName = FEOpts.ModuleLinkName;
   SerializationOpts.AutolinkForceLoad =

test/ModuleInterface/Inputs/dynamic.swiftinterface

@@ -0,0 +1,7 @@
+// swift-interface-format-version: 1.0
+// swift-module-flags: -module-name dynamic
+
+import Swift
+
+public func f() {}
+

test/ModuleInterface/Inputs/static.swiftinterface

@@ -0,0 +1,6 @@
+// swift-interface-format-version: 1.0
+// swift-module-flags: -static -module-name static
+
+import Swift
+
+public func f() {}

test/ModuleInterface/swift-interface-compile.swift

@@ -0,0 +1,14 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend -module-cache-path %t/mcp -I %S/Inputs -c %s -o /dev/null -D STATIC
+// RUN: llvm-bcanalyzer -dump %t/mcp/static-*.swiftmodule | %FileCheck %s -check-prefix CHECK-STATIC
+// RUN: %target-swift-frontend -module-cache-path %t/mcp -I %S/Inputs -c %s -o /dev/null
+// RUN: llvm-bcanalyzer -dump %t/mcp/dynamic-*.swiftmodule | %FileCheck %s -check-prefix CHECK-DYNAMIC
+
+#if STATIC
+import `static`
+#else
+import `dynamic`
+#endif
+
+// CHECK-STATIC: IS_STATIC
+// CHECK-DYNAMIC-NOT: IS_STATIC