diff --git a/pkgs/development/compilers/llvm/10/compiler-rt.nix b/pkgs/development/compilers/llvm/10/compiler-rt.nix
index 47bbe808ac2..e6882cbabb8 100644
--- a/pkgs/development/compilers/llvm/10/compiler-rt.nix
+++ b/pkgs/development/compilers/llvm/10/compiler-rt.nix
@@ -41,6 +41,11 @@ stdenv.mkDerivation rec {
     "-DCMAKE_TRY_COMPILE_TARGET_TYPE=STATIC_LIBRARY"
   ] ++ stdenv.lib.optionals (bareMetal) [
     "-DCOMPILER_RT_OS_DIR=baremetal"
+  ] ++ stdenv.lib.optionals (stdenv.hostPlatform.isDarwin) [
+    # The compiler-rt build infrastructure sniffs supported platforms on Darwin
+    # and finds i386;x86_64;x86_64h. We only build for x86_64, so linking fails
+    # when it tries to use libc++ and libc++api for i386.
+    "-DDARWIN_osx_ARCHS=${stdenv.hostPlatform.parsed.cpu.name}"
   ];
 
   outputs = [ "out" "dev" ];
diff --git a/pkgs/development/compilers/llvm/5/compiler-rt.nix b/pkgs/development/compilers/llvm/5/compiler-rt.nix
index 32d6dd3d479..41f2b24b057 100644
--- a/pkgs/development/compilers/llvm/5/compiler-rt.nix
+++ b/pkgs/development/compilers/llvm/5/compiler-rt.nix
@@ -41,6 +41,11 @@ stdenv.mkDerivation {
     "-DCMAKE_TRY_COMPILE_TARGET_TYPE=STATIC_LIBRARY"
   ] ++ stdenv.lib.optionals (bareMetal) [
     "-DCOMPILER_RT_OS_DIR=baremetal"
+  ] ++ stdenv.lib.optionals (stdenv.hostPlatform.isDarwin) [
+    # The compiler-rt build infrastructure sniffs supported platforms on Darwin
+    # and finds i386;x86_64;x86_64h. We only build for x86_64, so linking fails
+    # when it tries to use libc++ and libc++api for i386.
+    "-DDARWIN_osx_ARCHS=${stdenv.hostPlatform.parsed.cpu.name}"
   ];
 
   outputs = [ "out" "dev" ];
diff --git a/pkgs/development/compilers/llvm/6/compiler-rt.nix b/pkgs/development/compilers/llvm/6/compiler-rt.nix
index 89f25cad2c5..8bd61f5d7f7 100644
--- a/pkgs/development/compilers/llvm/6/compiler-rt.nix
+++ b/pkgs/development/compilers/llvm/6/compiler-rt.nix
@@ -41,6 +41,11 @@ stdenv.mkDerivation {
     "-DCMAKE_TRY_COMPILE_TARGET_TYPE=STATIC_LIBRARY"
   ] ++ stdenv.lib.optionals (bareMetal) [
     "-DCOMPILER_RT_OS_DIR=baremetal"
+  ] ++ stdenv.lib.optionals (stdenv.hostPlatform.isDarwin) [
+    # The compiler-rt build infrastructure sniffs supported platforms on Darwin
+    # and finds i386;x86_64;x86_64h. We only build for x86_64, so linking fails
+    # when it tries to use libc++ and libc++api for i386.
+    "-DDARWIN_osx_ARCHS=${stdenv.hostPlatform.parsed.cpu.name}"
   ];
 
   outputs = [ "out" "dev" ];
diff --git a/pkgs/development/compilers/llvm/7/compiler-rt.nix b/pkgs/development/compilers/llvm/7/compiler-rt.nix
index 97a5d73f304..ec9b7e6e6ad 100644
--- a/pkgs/development/compilers/llvm/7/compiler-rt.nix
+++ b/pkgs/development/compilers/llvm/7/compiler-rt.nix
@@ -41,6 +41,11 @@ stdenv.mkDerivation {
     "-DCMAKE_TRY_COMPILE_TARGET_TYPE=STATIC_LIBRARY"
   ] ++ stdenv.lib.optionals (bareMetal) [
     "-DCOMPILER_RT_OS_DIR=baremetal"
+  ] ++ stdenv.lib.optionals (stdenv.hostPlatform.isDarwin) [
+    # The compiler-rt build infrastructure sniffs supported platforms on Darwin
+    # and finds i386;x86_64;x86_64h. We only build for x86_64, so linking fails
+    # when it tries to use libc++ and libc++api for i386.
+    "-DDARWIN_osx_ARCHS=${stdenv.hostPlatform.parsed.cpu.name}"
   ];
 
   outputs = [ "out" "dev" ];
diff --git a/pkgs/development/compilers/llvm/8/compiler-rt.nix b/pkgs/development/compilers/llvm/8/compiler-rt.nix
index a907d408655..3c6265c4fca 100644
--- a/pkgs/development/compilers/llvm/8/compiler-rt.nix
+++ b/pkgs/development/compilers/llvm/8/compiler-rt.nix
@@ -41,6 +41,11 @@ stdenv.mkDerivation {
     "-DCMAKE_TRY_COMPILE_TARGET_TYPE=STATIC_LIBRARY"
   ] ++ stdenv.lib.optionals (bareMetal) [
     "-DCOMPILER_RT_OS_DIR=baremetal"
+  ] ++ stdenv.lib.optionals (stdenv.hostPlatform.isDarwin) [
+    # The compiler-rt build infrastructure sniffs supported platforms on Darwin
+    # and finds i386;x86_64;x86_64h. We only build for x86_64, so linking fails
+    # when it tries to use libc++ and libc++api for i386.
+    "-DDARWIN_osx_ARCHS=${stdenv.hostPlatform.parsed.cpu.name}"
   ];
 
   outputs = [ "out" "dev" ];
diff --git a/pkgs/development/compilers/llvm/9/compiler-rt.nix b/pkgs/development/compilers/llvm/9/compiler-rt.nix
index 394f66ff7f1..13b0b522771 100644
--- a/pkgs/development/compilers/llvm/9/compiler-rt.nix
+++ b/pkgs/development/compilers/llvm/9/compiler-rt.nix
@@ -41,6 +41,11 @@ stdenv.mkDerivation rec {
     "-DCMAKE_TRY_COMPILE_TARGET_TYPE=STATIC_LIBRARY"
   ] ++ stdenv.lib.optionals (bareMetal) [
     "-DCOMPILER_RT_OS_DIR=baremetal"
+  ] ++ stdenv.lib.optionals (stdenv.hostPlatform.isDarwin) [
+    # The compiler-rt build infrastructure sniffs supported platforms on Darwin
+    # and finds i386;x86_64;x86_64h. We only build for x86_64, so linking fails
+    # when it tries to use libc++ and libc++api for i386.
+    "-DDARWIN_osx_ARCHS=${stdenv.hostPlatform.parsed.cpu.name}"
   ];
 
   outputs = [ "out" "dev" ];