buildRustPackage: fix cargoBuildFlags

When features were supplied in cargoBuildFlags, the binaries were built
with these features enabled. Unless checking was disabled, `cargo test`
was executed without these build flags, meaning the binaries were
rebuilt and overwritten without the specified features.

Fix this bug by running tests after the installation phase.

pkgs/build-support/rust/default.nix

@@ -199,7 +199,7 @@ stdenv.mkDerivation (args // {
       -executable ! \( -regex ".*\.\(so.[0-9.]+\|so\|a\|dylib\)" \))
   '';
 
-  checkPhase = args.checkPhase or (let
+  installCheckPhase = args.checkPhase or (let
     argstr = "${stdenv.lib.optionalString (checkType == "release") "--release"} --target ${rustTarget} --frozen";
   in ''
     ${stdenv.lib.optionalString (buildAndTestSubdir != null) "pushd ${buildAndTestSubdir}"}

pkgs/development/tools/rust/rustup/default.nix

@@ -39,7 +39,9 @@ rustPlatform.buildRustPackage rec {
     )
   ];
 
-  doCheck = !stdenv.isAarch64 && !stdenv.isDarwin;
+  # Disable tests until they can be run with --features no-self-update
+  doCheck = false;
+  #doCheck = !stdenv.isAarch64 && !stdenv.isDarwin;
 
   postInstall = ''
     pushd $out/bin