Allow enabling core dumps from builds for nix & child processes

Fixes https://git.lix.systems/lix-project/lix/issues/268

Change-Id: I3f1b0ddf064f891cca8b53229c5c31c74cea3d9f

src/libstore/build/local-derivation-goal.cc

@@ -1977,6 +1977,9 @@ void LocalDerivationGoal::runChild()
 
         /* Disable core dumps by default. */
         struct rlimit limit = { 0, RLIM_INFINITY };
+        if (settings.enableCoreDumps) {
+            limit.rlim_cur = RLIM_INFINITY;
+        }
         setrlimit(RLIMIT_CORE, &limit);
 
         // FIXME: set other limits to deterministic values?

src/libstore/globals.hh

@@ -290,6 +290,15 @@ public:
     Setting<off_t> reservedSize{this, 8 * 1024 * 1024, "gc-reserved-space",
         "Amount of reserved disk space for the garbage collector."};
 
+    Setting<bool> enableCoreDumps{
+        this, false, "enable-core-dumps",
+        R"(
+          If set to `false` (the default), `RLIMIT_CORE` has a soft limit of zero.
+          If set to `true`, the soft limit is infinite.
+
+          The hard limit is always infinite.
+        )"};
+
     Setting<bool> fsyncMetadata{
         this, true, "fsync-metadata",
         R"(