Use cpio instead of python for install script

rust-installer.py

@@ -1,27 +0,0 @@
-# The install script for rust components.
-# Some toolchains have tons of install directives which makes bash script too slow.
-import os
-from pathlib import Path
-from shutil import copy, copytree
-
-out = Path(os.environ['out'])
-verbose = os.environ.get('VERBOSE_INSTALL') == '1'
-
-installer_version = int(Path('./rust-installer-version').read_text().strip())
-if installer_version == 3:
-    for component in Path('./components').read_text().splitlines():
-        print(f'Installing component {component}')
-        for directive in (Path(component) / 'manifest.in').read_text().splitlines():
-            cmd, file = directive.split(':')
-            in_file, out_file = Path(component) / file, out / file
-            out_file.parent.mkdir(parents=True, exist_ok=True)
-            if verbose:
-                print(f'Installing {cmd}: {file}')
-            if cmd == 'file':
-                copy(in_file, out_file)
-            elif cmd == 'dir':
-                copytree(in_file, out_file)
-            else:
-                assert False, f'Unknown command: {cmd}'
-else:
-    assert False, f'Unknown installer version: {installer_version}'

rust-overlay.nix

@@ -183,13 +183,19 @@ let
       # entire unpacked contents after just a little twiddling.
       preferLocalBuild = true;
 
-      nativeBuildInputs = [ self.python3 ];
-
-      # VERBOSE_INSTALL = 1; # No spam by default.
+      nativeBuildInputs = [ self.cpio ];
 
       installPhase = ''
         runHook preInstall
-        python3 ${./rust-installer.py}
+        installerVersion=$(< ./rust-installer-version)
+        if [[ "$installerVersion" != 3 ]]; then
+          echo "Unknown installer version: $installerVersion"
+        fi
+        while read -r comp; do
+          echo "Installing component $comp"
+          # Use cpio with file list instead of forking tons of cp.
+          cut -d: -f2 <"$comp/manifest.in" | cpio --quiet -pdD "$comp" "$out"
+        done <./components
         runHook postInstall
       '';