compiler-rt: prevent platform sniffing on Darwin

Exposed by the tbd stubs which contains fat libraries. The previously
used proxy libraries were x86_64 only.

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" ];

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" ];

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" ];

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" ];

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" ];

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" ];