prometheus: fix cross-build

pkgs/by-name/pr/prometheus/package.nix

@@ -1,5 +1,6 @@
 {
   stdenv,
+  buildPackages,
   lib,
   go,
   buildGoModule,
@@ -48,6 +49,8 @@ buildGoModule (finalAttrs: {
     hash = "sha256-hRuZxwPPDLxQvy5MPKEyfmanNabcSjLRO+XbNKugPtk=";
   };
 
+  depsBuildBuild = [ buildPackages.stdenv.cc ];
+
   vendorHash = "sha256-5wDaG01vcTtGzrS/S33U5XWXoSWM+N9z3dzXZlILxD8=";
 
   webUiStatic = fetchurl {
@@ -96,7 +99,9 @@ buildGoModule (finalAttrs: {
   '';
 
   preBuild = ''
-    if [[ -d vendor ]]; then GOARCH= make -o assets assets-compress plugins; fi
+    if [[ -d vendor ]]; then
+      GOARCH= CC="$CC_FOR_BUILD" LD="$LD_FOR_BUILD" make -o assets assets-compress plugins
+    fi
   '';
 
   tags = [ "builtinassets" ];