Rustup to rustc 1.39.0-nightly (f0b58fc 2019-09-11)

Author: bjorn3

build_sysroot/Cargo.toml

@@ -7,7 +7,7 @@ version = "0.0.0"
 core = { path = "./sysroot_src/src/libcore" }
 compiler_builtins = "0.1"
 alloc = { path = "./sysroot_src/src/liballoc" }
-std = { path = "./sysroot_src/src/libstd", features = ["panic_unwind"] }
+std = { path = "./sysroot_src/src/libstd", features = ["panic_unwind", "backtrace"] }
 test = { path = "./sysroot_src/src/libtest" }
 
 alloc_system = { path = "./alloc_system" }