Set backup MANPATH in case man path isn’t set correctly.

Previously, this would fail at startup for non-NixOS installs:

nix-env --help

The fix for this is to just use "nixManDir" as the value for MANPATH
when spawning "man".

To test this, I’m using the following:

$ nix-build release.nix -A build
$ MANPATH= ./result/bin/nix-env --help

Fixes #1627

1 files changed, 3 insertions, 0 deletions

diff --git a/src/libstore/globals.hh b/src/libstore/globals.hh
index 508084d08acb..fd3fbec9f017 100644
--- a/src/libstore/globals.hh
+++ b/src/libstore/globals.hh
@@ -82,6 +82,9 @@ public:
     /* The directory where the main programs are stored. */
     Path nixBinDir;
 
+    /* The directory where the man pages are stored. */
+    Path nixManDir;
+
     /* File name of the socket the daemon listens to.  */
     Path nixDaemonSocketFile;