nixpkgs/pkgs/development/compilers/swift/compiler/patches/swift-separate-lib.patch

Patch paths to use the separate 'lib' output. One of the things this patch
fixes is the output of `swift -frontend -print-target-info`, which swiftpm uses
to set rpath on Linux.

The check if the executable path starts with 'out' is necessary for
bootstrapping, or the compiler will fail when run from the build directory.

--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -49,11 +49,16 @@ swift::CompilerInvocation::CompilerInvocation() {
 void CompilerInvocation::computeRuntimeResourcePathFromExecutablePath(
     StringRef mainExecutablePath, bool shared,
     llvm::SmallVectorImpl<char> &runtimeResourcePath) {
+  if (mainExecutablePath.startswith("@storeDir@")) {
+    auto libPath = StringRef("@lib@");
+    runtimeResourcePath.append(libPath.begin(), libPath.end());
+  } else {
   runtimeResourcePath.append(mainExecutablePath.begin(),
                              mainExecutablePath.end());
 
   llvm::sys::path::remove_filename(runtimeResourcePath); // Remove /swift
   llvm::sys::path::remove_filename(runtimeResourcePath); // Remove /bin
+  }
   appendSwiftLibDir(runtimeResourcePath, shared);
 }