csmith: move CXXFLAGS into env for structuredAttrs

pkgs/by-name/cl/clfft/package.nix

@@ -46,7 +46,7 @@ stdenv.mkDerivation (finalAttrs: {
   ];
 
   # https://github.com/clMathLibraries/clFFT/issues/237
-  CXXFLAGS = "-std=c++98";
+  env.CXXFLAGS = "-std=c++98";
 
   meta = {
     description = "Library containing FFT functions written in OpenCL";

pkgs/by-name/cr/cryptopp/package.nix

@@ -42,7 +42,10 @@ stdenv.mkDerivation rec {
 
   enableParallelBuilding = true;
   hardeningDisable = [ "fortify" ];
-  CXXFLAGS = lib.optionals withOpenMP [ "-fopenmp" ];
+
+  env = lib.optionalAttrs withOpenMP {
+    CXXFLAGS = "-fopenmp";
+  };
 
   doCheck = true;
 

pkgs/by-name/cs/csmith/package.nix

@@ -29,7 +29,7 @@ stdenv.mkDerivation rec {
     SysCPU
   ]);
 
-  CXXFLAGS = "-std=c++98";
+  env.CXXFLAGS = "-std=c++98";
 
   postInstall = ''
     substituteInPlace $out/bin/compiler_test.pl \