daemon: Bind-mount /etc/nsswitch.conf & co. only if it exists.

Those files may be missing in some contexts, for instance within the
build environment.

* nix/libstore/build.cc (DerivationGoal::runChild): Add /etc/resolv.conf
and related files to ‘ss’ only if they exist.

Change-Id: Ie19664a86c8101a1dc82cf39ad4b7abb10f8250a

1 files changed, 5 insertions, 4 deletions

diff --git a/nix/libstore/build.cc b/nix/libstore/build.cc
index edd01bab34..8ca5e5b732 100644
--- a/nix/libstore/build.cc
+++ b/nix/libstore/build.cc
@@ -2093,10 +2093,11 @@ void DerivationGoal::runChild()
                network, so give them access to /etc/resolv.conf and so
                on. */
             if (fixedOutput) {
-                ss.push_back("/etc/resolv.conf");
-                ss.push_back("/etc/nsswitch.conf");
-                ss.push_back("/etc/services");
-                ss.push_back("/etc/hosts");
+		auto files = { "/etc/resolv.conf", "/etc/nsswitch.conf",
+			       "/etc/services", "/etc/hosts" };
+		for (auto & file: files) {
+		    if (pathExists(file)) ss.push_back(file);
+		}
             }
 
             for (auto & i : ss) dirsInChroot[i] = i;