earlyoom: fix version number (#46481)

earlyoom's Makefile attempts to detect the current version using git,
but we don't keep .git in its source, so this fails. We can however
set the VERSION environment variable to override this, as we now do.

pkgs/os-specific/linux/earlyoom/default.nix

@@ -1,19 +1,19 @@
 { lib, stdenv, fetchFromGitHub }:
 
 stdenv.mkDerivation rec {
-  name = "earlyoom-${version}";
-  version = "0.11";
+  name = "earlyoom-${VERSION}";
+  # This environment variable is read by make to set the build version.
+  VERSION = "0.11";
 
   src = fetchFromGitHub {
     owner = "rfjakob";
     repo = "earlyoom";
-    rev = "08b7ed8e72feed2eec2e558ba2cfacbf6d469594";
+    rev = "v${VERSION}";
     sha256 = "1k3xslb70fzk80wlka32l0k2v45qn1xgwyjkjiz85gv6v4mv92vl";
   };
 
   installPhase = ''
-    mkdir -p $out/bin
-    cp earlyoom $out/bin
+    install -D earlyoom $out/bin/earlyoom
   '';
 
   meta = {