Set RLIMIT_CORE to 0, infinity in builders

This prevents the builder from being affected by whatever the host
system limits happen to be.

src/libstore/build.cc

@@ -22,6 +22,7 @@
 #include <sys/stat.h>
 #include <sys/utsname.h>
 #include <sys/select.h>
+#include <sys/resource.h>
 #include <fcntl.h>
 #include <unistd.h>
 #include <errno.h>
@@ -2373,6 +2374,12 @@ void DerivationGoal::runChild()
         if (cur != -1) personality(cur | ADDR_NO_RANDOMIZE);
 #endif
 
+        /* Disable core dumps by default. */
+        struct rlimit limit = { 0, RLIM_INFINITY };
+        setrlimit(RLIMIT_CORE, &limit);
+
+        // FIXME: set other limits to deterministic values?
+
         /* Fill in the environment. */
         Strings envStrs;
         for (auto & i : env)