Use RUNPATH instead of RPATH so that end users can override the library
search path (and the 'validate-runpath' phase can do its work).

diff --git a/build/config/gcc/BUILD.gn b/build/config/gcc/BUILD.gn
--- a/build/config/gcc/BUILD.gn
+++ b/build/config/gcc/BUILD.gn
@@ -99,7 +99,14 @@ config("executable_config") {
     ]
   }
 
-  if (!is_android && current_os != "aix") {
+  if (is_linux) {
+    ldflags += [
+      # Set DT_RUNPATH instead of DT_RPATH which is important because the
+      # former can be overridden at runtime, and Guix has support for
+      # verifying that nothing is missing.
+      "-Wl,--enable-new-dtags",
+    ]
+  } else if (!is_android && current_os != "aix") {
     ldflags += [
       # TODO(GYP): Do we need a check on the binutils version here?
       #