buildRustPackage: fix regex for separating lib and bin

E.g. exa was wrongly put into /lib, as it matches

  .*.a

but not

  .*\.a

pkgs/build-support/rust/default.nix

@@ -92,8 +92,8 @@ in stdenv.mkDerivation (args // {
   installPhase = args.installPhase or ''
     runHook preInstall
     mkdir -p $out/bin $out/lib
-    find target/release -maxdepth 1 -type f -executable ! \( -regex ".*.\(so.[0-9.]+\|so\|a\|dylib\)" \) -print0 | xargs -r -0 cp -t $out/bin
-    find target/release -maxdepth 1 -regex ".*.\(so.[0-9.]+\|so\|a\|dylib\)" -print0 | xargs -r -0 cp -t $out/lib
+    find target/release -maxdepth 1 -type f -executable ! \( -regex ".*\.\(so.[0-9.]+\|so\|a\|dylib\)" \) -print0 | xargs -r -0 cp -t $out/bin
+    find target/release -maxdepth 1 -regex ".*\.\(so.[0-9.]+\|so\|a\|dylib\)" -print0 | xargs -r -0 cp -t $out/lib
     rmdir --ignore-fail-on-non-empty $out/lib $out/bin
     runHook postInstall
   '';