miri needs to be *built* with RUST_SYSROOT, not *run*

.travis.yml

@@ -7,7 +7,7 @@ before_script:
   export PATH=$HOME/.local/bin:$PATH
 script:
 - |
-  travis-cargo build &&
+  env RUST_SYSROOT=$HOME/rust travis-cargo build &&
   env RUST_SYSROOT=$HOME/rust travis-cargo test
 notifications:
   email:

tests/compiletest.rs

@@ -63,7 +63,6 @@ fn compile_test() {
             cmd.arg(format!("--sysroot={}", sysroot));
             cmd.arg("-Dwarnings");
             cmd.arg(format!("--target={}", target));
-            cmd.env("RUST_SYSROOT", &sysroot);
             let libs = Path::new(&sysroot).join("lib");
             let sysroot = libs.join("rustlib").join(&target).join("lib");
             let paths = std::env::join_paths(&[libs, sysroot]).unwrap();