tests: update compiler-builtins

Update `run-make/compiler-builtins` to not use `Command::env_clear`
for `cargo` to not mess up temp dir on Windows platforms, which need
to be set in order for codegen temp files to function properly.
Otherwise, if the temp dir falls back to the Windows directory, there
will be permission errors (let alone having temp files in non-build
directories).

tests/run-make/compiler-builtins/rmake.rs

@@ -14,6 +14,7 @@
 
 #![deny(warnings)]
 
+use run_make_support::clear_non_essential_env_vars;
 use run_make_support::object;
 use run_make_support::object::read::archive::ArchiveFile;
 use run_make_support::object::read::Object;
@@ -48,6 +49,10 @@ fn main() {
     let rustc = std::env::var("RUSTC").unwrap();
     let bootstrap_cargo = std::env::var("BOOTSTRAP_CARGO").unwrap();
     let mut cmd = std::process::Command::new(bootstrap_cargo);
+
+    // Remove some env vars inherited from parent processes to fully control the env vars
+    // `cargo` has access to.
+    clear_non_essential_env_vars(&mut cmd);
     cmd.args([
         "build",
         "--manifest-path",
@@ -56,7 +61,6 @@ fn main() {
         "--target",
         &target,
     ])
-    .env_clear()
     .env("PATH", path)
     .env("RUSTC", rustc)
     .env("RUSTFLAGS", "-Copt-level=0 -Cdebug-assertions=yes")