Don't apply the CPU affinity hack to nix-shell (and other Perl programs)

As discovered by Todd Veldhuizen, the shell started by nix-shell has
its affinity set to a single CPU.  This is because nix-shell connects
to the Nix daemon, which causes the affinity hack to be applied.  So
we turn this off for Perl programs.

1 files changed, 1 insertions, 0 deletions

diff --git a/src/libstore/globals.cc b/src/libstore/globals.cc
index aeb52e1a8696..7e0157cd365a 100644
--- a/src/libstore/globals.cc
+++ b/src/libstore/globals.cc
@@ -54,6 +54,7 @@ Settings::Settings()
     gcKeepDerivations = true;
     autoOptimiseStore = false;
     envKeepDerivations = false;
+    lockCPU = getEnv("NIX_AFFINITY_HACK", "1") == "1";
 }