swiftPackages.stdenv: use the default standard environment

Swift now works fine with standard environments using GCC or other
versions of LLVM. Some packages, like components of Swift itself or
others that combine Swift with features like C++ modules or C blocks,
may still need to use an LLVM‐based standard environment, but we
do not need to enforce a uniform `swiftPackages.stdenv` any more.

pkgs/development/compilers/swift/default.nix

@@ -1,43 +1,21 @@
 {
   lib,
-  pkgs,
   newScope,
-  darwin,
+  stdenv,
   llvmPackages,
-  overrideCC,
-  overrideLibcxx,
+  darwin,
 }:
 
 let
-  swiftLlvmPackages = llvmPackages;
-
   self = rec {
 
     callPackage = newScope self;
 
-    # Swift builds its own Clang for internal use. We wrap that clang with a
-    # cc-wrapper derived from the clang configured below. Because cc-wrapper
-    # applies a specific resource-root, the two versions are best matched, or
-    # we'll often run into compilation errors.
-    #
-    # The following selects the correct Clang version, matching the version
-    # used in Swift.
-    inherit (swiftLlvmPackages) clang;
-
-    # Overrides that create a useful environment for swift packages, allowing
-    # packaging with `swiftPackages.callPackage`.
-    inherit (clang) bintools;
-    stdenv =
-      let
-        stdenv' = overrideCC pkgs.stdenv clang;
-      in
-      # Ensure that Swift’s internal clang uses the same libc++ and libc++abi as the
-      # default clang’s stdenv. Using the default libc++ avoids issues (such as crashes)
-      # that can happen when a Swift application dynamically links different versions
-      # of libc++ and libc++abi than libraries it links are using.
-      if stdenv'.cc.libcxx != null then overrideLibcxx stdenv' else stdenv';
+    # Provided for backwards compatibility.
+    inherit stdenv;
 
     swift-unwrapped = callPackage ./compiler {
+      inherit (llvmPackages) stdenv;
       inherit (darwin) DarwinTools sigtool;
     };
 
@@ -50,13 +28,19 @@ let
       if stdenv.hostPlatform.isDarwin then
         null # part of apple-sdk
       else
-        callPackage ./libdispatch { swift = swiftNoSwiftDriver; };
+        callPackage ./libdispatch {
+          inherit (llvmPackages) stdenv;
+          swift = swiftNoSwiftDriver;
+        };
 
     Foundation =
       if stdenv.hostPlatform.isDarwin then
         null # part of apple-sdk
       else
-        callPackage ./foundation { swift = swiftNoSwiftDriver; };
+        callPackage ./foundation {
+          inherit (llvmPackages) stdenv;
+          swift = swiftNoSwiftDriver;
+        };
 
     # TODO: Apple distributes a binary XCTest with Xcode, but it is not part of
     # CLTools (or SUS), so would have to figure out how to fetch it. The binary
@@ -67,11 +51,13 @@ let
     };
 
     swiftpm = callPackage ./swiftpm {
+      inherit (llvmPackages) stdenv;
       inherit (darwin) DarwinTools;
       swift = swiftNoSwiftDriver;
     };
 
     swift-driver = callPackage ./swift-driver {
+      inherit (llvmPackages) stdenv;
       swift = swiftNoSwiftDriver;
     };
 
@@ -79,11 +65,17 @@ let
       swift = swift-unwrapped;
     };
 
-    sourcekit-lsp = callPackage ./sourcekit-lsp { };
+    sourcekit-lsp = callPackage ./sourcekit-lsp {
+      inherit (llvmPackages) stdenv;
+    };
 
-    swift-docc = callPackage ./swift-docc { };
+    swift-docc = callPackage ./swift-docc {
+      inherit (llvmPackages) stdenv;
+    };
 
-    swift-format = callPackage ./swift-format { };
+    swift-format = callPackage ./swift-format {
+      inherit (llvmPackages) stdenv;
+    };
 
     swiftpm2nix = callPackage ./swiftpm2nix { };