From a333210fdc00f9891db773ff857860a8e9f7bd1e Mon Sep 17 00:00:00 2001
From: Rodrigo Arias Mallo <rodrigo.arias@bsc.es>
Date: Fri, 19 Jan 2024 17:10:22 +0100
Subject: [PATCH] Only change cross stdenv

Prevents mass rebuilds in x86, where the envvar doesn't have any effect.
---
 overlay.nix | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/overlay.nix b/overlay.nix
index 9cc6df6..6578708 100644
--- a/overlay.nix
+++ b/overlay.nix
@@ -33,9 +33,13 @@ final: prev:
 
   # To cross compile for riscv64, we need to populate this env variable, not
   # NIX_CFLAGS_COMPILE, otherwise we affect the packages for x86.
-  stdenv = prev.stdenvAdapters.addAttrsToDerivation {
-    NIX_CFLAGS_COMPILE_riscv64_unknown_linux_gnu = "-march=rv64g";
-  } prev.stdenv;
+  stdenv = if prev.stdenv.buildPlatform != prev.stdenv.hostPlatform
+  then
+    prev.stdenvAdapters.addAttrsToDerivation {
+      NIX_CFLAGS_COMPILE_riscv64_unknown_linux_gnu = "-march=rv64g";
+    } prev.stdenv
+  else
+    prev.stdenv;
 
   opensbi-uboot = prev.opensbi.overrideAttrs (old: {
     makeFlags = old.makeFlags ++ [