Add an option of using nix-shell instead of nix flake

Author: WaffleLapkin

.envrc

@@ -0,0 +1,8 @@
+# If you want to use this as an .envrc file to create a shell with necessery components 
+# to develop rustc, use the following command in the root of the rusr checkout:
+#	
+# ln -s ./src/tools/nix-dev-shell/envrc-flake ./.envrc && echo .envrc >> .git/info/exclude
+
+if nix flake show path:./src/tools/nix-dev-shell &> /dev/null; then
+ use flake path:./src/tools/nix-dev-shell
+fi

src/tools/nix-dev-shell/envrc-flake

@@ -0,0 +1,7 @@
+# If you want to use this as an .envrc file to create a shell with necessery components 
+# to develop rustc, use the following command in the root of the rusr checkout:
+#	
+# ln -s ./src/tools/nix-dev-shell/envrc-shell ./.envrc && echo .envrc >> .git/info/exclude
+
+use nix ./src/tools/nix-dev-shell/shell.nix
+

src/tools/nix-dev-shell/envrc-shell

@@ -0,0 +1,19 @@
+{pkgs ? import<nixpkgs>{}}:
+let
+x=import./x{inheritpkgs;};
+in
+pkgs.mkShell{
+name="rustc";
+nativeBuildInputs=withpkgs;[
+binutilscmakeninjapkg-configpython3gitcurlcacertpatchelfnix
+];
+buildInputs=withpkgs;[
+opensslglibc.outglibc.staticx
+];
+# Avoid creating text files for ICEs.
+RUSTC_ICE="0";
+# Provide `libstdc++.so.6` for the self-contained lld.
+LD_LIBRARY_PATH="${withpkgs;lib.makeLibraryPath[
+stdenv.cc.cc.lib
+]}";
+}