diff --git a/pkgs/development/compilers/llvm/10/default.nix b/pkgs/development/compilers/llvm/10/default.nix
index 83840b4fd27e..5cb6c278659d 100644
--- a/pkgs/development/compilers/llvm/10/default.nix
+++ b/pkgs/development/compilers/llvm/10/default.nix
@@ -91,8 +91,8 @@ let
 
     # pick clang appropriate for package set we are targeting
     clang =
-      if (pkgs.targetPackages.stdenv or stdenv).cc.isGNU
-      then tools.libstdcxxClang
+      /**/ if stdenv.targetPlatform.useLLVM or false then tools.clangUseLLVM
+      else if (pkgs.targetPackages.stdenv or stdenv).cc.isGNU then tools.libstdcxxClang
       else tools.libcxxClang;
 
     libstdcxxClang = wrapCCWith rec {
diff --git a/pkgs/development/compilers/llvm/11/default.nix b/pkgs/development/compilers/llvm/11/default.nix
index b5c070915242..82a78af85cac 100644
--- a/pkgs/development/compilers/llvm/11/default.nix
+++ b/pkgs/development/compilers/llvm/11/default.nix
@@ -106,8 +106,8 @@ let
 
     # pick clang appropriate for package set we are targeting
     clang =
-      if (pkgs.targetPackages.stdenv or stdenv).cc.isGNU
-      then tools.libstdcxxClang
+      /**/ if stdenv.targetPlatform.useLLVM or false then tools.clangUseLLVM
+      else if (pkgs.targetPackages.stdenv or stdenv).cc.isGNU then tools.libstdcxxClang
       else tools.libcxxClang;
 
     libstdcxxClang = wrapCCWith rec {
diff --git a/pkgs/development/compilers/llvm/12/default.nix b/pkgs/development/compilers/llvm/12/default.nix
index 8de6bb420d41..4a2a7ee87894 100644
--- a/pkgs/development/compilers/llvm/12/default.nix
+++ b/pkgs/development/compilers/llvm/12/default.nix
@@ -94,8 +94,8 @@ let
 
     # pick clang appropriate for package set we are targeting
     clang =
-      if (pkgs.targetPackages.stdenv or stdenv).cc.isGNU
-      then tools.libstdcxxClang
+      /**/ if stdenv.targetPlatform.useLLVM or false then tools.clangUseLLVM
+      else if (pkgs.targetPackages.stdenv or stdenv).cc.isGNU then tools.libstdcxxClang
       else tools.libcxxClang;
 
     libstdcxxClang = wrapCCWith rec {
diff --git a/pkgs/development/compilers/llvm/13/default.nix b/pkgs/development/compilers/llvm/13/default.nix
index bdc07a68742d..be5e9404cdd4 100644
--- a/pkgs/development/compilers/llvm/13/default.nix
+++ b/pkgs/development/compilers/llvm/13/default.nix
@@ -95,8 +95,8 @@ let
 
     # pick clang appropriate for package set we are targeting
     clang =
-      if (pkgs.targetPackages.stdenv or stdenv).cc.isGNU
-      then tools.libstdcxxClang
+      /**/ if stdenv.targetPlatform.useLLVM or false then tools.clangUseLLVM
+      else if (pkgs.targetPackages.stdenv or stdenv).cc.isGNU then tools.libstdcxxClang
       else tools.libcxxClang;
 
     libstdcxxClang = wrapCCWith rec {
diff --git a/pkgs/development/compilers/llvm/5/default.nix b/pkgs/development/compilers/llvm/5/default.nix
index 4a6d55d55727..ef9886fb5ea7 100644
--- a/pkgs/development/compilers/llvm/5/default.nix
+++ b/pkgs/development/compilers/llvm/5/default.nix
@@ -67,8 +67,8 @@ let
 
     # pick clang appropriate for package set we are targeting
     clang =
-      if (pkgs.targetPackages.stdenv or stdenv).cc.isGNU
-      then tools.libstdcxxClang
+      /**/ if stdenv.targetPlatform.useLLVM or false then tools.clangUseLLVM
+      else if (pkgs.targetPackages.stdenv or stdenv).cc.isGNU then tools.libstdcxxClang
       else tools.libcxxClang;
 
     libstdcxxClang = wrapCCWith rec {
diff --git a/pkgs/development/compilers/llvm/6/default.nix b/pkgs/development/compilers/llvm/6/default.nix
index 1b9a793e8858..4acfe6cd85d7 100644
--- a/pkgs/development/compilers/llvm/6/default.nix
+++ b/pkgs/development/compilers/llvm/6/default.nix
@@ -68,8 +68,8 @@ let
 
     # pick clang appropriate for package set we are targeting
     clang =
-      if (pkgs.targetPackages.stdenv or stdenv).cc.isGNU
-      then tools.libstdcxxClang
+      /**/ if stdenv.targetPlatform.useLLVM or false then tools.clangUseLLVM
+      else if (pkgs.targetPackages.stdenv or stdenv).cc.isGNU then tools.libstdcxxClang
       else tools.libcxxClang;
 
     libstdcxxClang = wrapCCWith rec {
diff --git a/pkgs/development/compilers/llvm/7/default.nix b/pkgs/development/compilers/llvm/7/default.nix
index 841fc120d744..f0908f30775d 100644
--- a/pkgs/development/compilers/llvm/7/default.nix
+++ b/pkgs/development/compilers/llvm/7/default.nix
@@ -98,8 +98,8 @@ let
 
     # pick clang appropriate for package set we are targeting
     clang =
-      if (pkgs.targetPackages.stdenv or stdenv).cc.isGNU
-      then tools.libstdcxxClang
+      /**/ if stdenv.targetPlatform.useLLVM or false then tools.clangUseLLVM
+      else if (pkgs.targetPackages.stdenv or stdenv).cc.isGNU then tools.libstdcxxClang
       else tools.libcxxClang;
 
     libstdcxxClang = wrapCCWith rec {
diff --git a/pkgs/development/compilers/llvm/8/default.nix b/pkgs/development/compilers/llvm/8/default.nix
index 234473c1adae..43050a72b922 100644
--- a/pkgs/development/compilers/llvm/8/default.nix
+++ b/pkgs/development/compilers/llvm/8/default.nix
@@ -99,8 +99,8 @@ let
 
     # pick clang appropriate for package set we are targeting
     clang =
-      if (pkgs.targetPackages.stdenv or stdenv).cc.isGNU
-      then tools.libstdcxxClang
+      /**/ if stdenv.targetPlatform.useLLVM or false then tools.clangUseLLVM
+      else if (pkgs.targetPackages.stdenv or stdenv).cc.isGNU then tools.libstdcxxClang
       else tools.libcxxClang;
 
     libstdcxxClang = wrapCCWith rec {
diff --git a/pkgs/development/compilers/llvm/9/default.nix b/pkgs/development/compilers/llvm/9/default.nix
index a10bac13824e..7efe8486a387 100644
--- a/pkgs/development/compilers/llvm/9/default.nix
+++ b/pkgs/development/compilers/llvm/9/default.nix
@@ -99,8 +99,8 @@ let
 
     # pick clang appropriate for package set we are targeting
     clang =
-      if (pkgs.targetPackages.stdenv or stdenv).cc.isGNU
-      then tools.libstdcxxClang
+      /**/ if stdenv.targetPlatform.useLLVM or false then tools.clangUseLLVM
+      else if (pkgs.targetPackages.stdenv or stdenv).cc.isGNU then tools.libstdcxxClang
       else tools.libcxxClang;
 
     libstdcxxClang = wrapCCWith rec {
diff --git a/pkgs/development/compilers/llvm/git/default.nix b/pkgs/development/compilers/llvm/git/default.nix
index 56904addb52b..890270c851db 100644
--- a/pkgs/development/compilers/llvm/git/default.nix
+++ b/pkgs/development/compilers/llvm/git/default.nix
@@ -95,8 +95,8 @@ let
 
     # pick clang appropriate for package set we are targeting
     clang =
-      if (pkgs.targetPackages.stdenv or stdenv).cc.isGNU
-      then tools.libstdcxxClang
+      /**/ if stdenv.targetPlatform.useLLVM or false then tools.clangUseLLVM
+      else if (pkgs.targetPackages.stdenv or stdenv).cc.isGNU then tools.libstdcxxClang
       else tools.libcxxClang;
 
     libstdcxxClang = wrapCCWith rec {