ethminer: use regular stdenv when CUDA isn't used

pkgs/tools/misc/ethminer/default.nix

@@ -1,5 +1,6 @@
 {
   lib,
+  stdenv,
   clangStdenv,
   fetchFromGitHub,
   opencl-headers,
@@ -16,11 +17,11 @@
   openssl,
   pkg-config,
   cli11
-}:
+}@args:
 
 # Note that this requires clang < 9.0 to build, and currently
 # clangStdenv provides clang 7.1 which satisfies the requirement.
-let stdenv = clangStdenv;
+let stdenv = if cudaSupport then clangStdenv else args.stdenv;
 
 in stdenv.mkDerivation rec {
   pname = "ethminer";