Add manditory data-layout field again

See rust-lang/rust#31367 (comment)

Author: phil-opp

float_free_target.json

@@ -2,6 +2,7 @@
   "llvm-target": "x86_64-unknown-none-gnu",
   "target-endian": "little",
   "target-pointer-width": "64",
+  "data-layout": "e-m:e-i64:64-f80:128-n8:16:32:64-S128",
   "os": "none",
   "arch": "x86_64",
   "pre-link-args": [ "-m64" ],