Add set_backtrace_level helper function to run_make_support

Author: Oneirical

src/tools/run-make-support/src/rustc.rs

@@ -100,6 +100,12 @@ impl Rustc {
         self
     }
 
+    //Adjust the backtrace level, displaying more detailed information at higher levels.
+    pub fn set_backtrace_level<R: AsRef<OsStr>>(&mut self, level: R) -> &mut Self {
+        self.cmd.env("RUST_BACKTRACE", level);
+        self
+    }
+
     /// Specify path to the output file. Equivalent to `-o`` in rustc.
     pub fn output<P: AsRef<Path>>(&mut self, path: P) -> &mut Self {
         self.cmd.arg("-o");

tests/run-make/short-ice/rmake.rs

@@ -5,15 +5,23 @@
 // See https://github.com/rust-lang/rust/issues/107910
 
 use run_make_support::rustc;
-use std::env;
 
 fn main() {
-    env::set_var("RUST_BACKTRACE", "1");
-    let mut rust_test_1 = rustc().input("src/lib.rs").arg("-Ztreat-err-as-bug=1").run_fail();
-    env::set_var("RUST_BACKTRACE", "full");
-    let mut rust_test_2 = rustc().input("src/lib.rs").arg("-Ztreat-err-as-bug=1").run_fail();
-    let rust_test_log_1 = rust_test_1.stderr_utf8().push_str(&rust_test_1.stdout_utf8()).as_str();
-    let rust_test_log_2 = rust_test_2.stderr_utf8().push_str(&rust_test_2.stdout_utf8()).as_str();
+    let rust_test_1 =
+        rustc().set_backtrace_level("1").input("src/lib.rs").arg("-Ztreat-err-as-bug=1").run_fail();
+    let rust_test_2 = rustc()
+        .set_backtrace_level("full")
+        .input("src/lib.rs")
+        .arg("-Ztreat-err-as-bug=1")
+        .run_fail();
+
+    let mut rust_test_log_1 = rust_test_1.stderr_utf8();
+    rust_test_log_1.push_str(&rust_test_1.stdout_utf8());
+    let rust_test_log_1 = rust_test_log_1.as_str();
+
+    let mut rust_test_log_2 = rust_test_2.stderr_utf8();
+    rust_test_log_2.push_str(&rust_test_2.stdout_utf8());
+    let rust_test_log_2 = rust_test_log_2.as_str();
 
     let rustc_query_count_full = count_lines_with(rust_test_log_2, "rustc_query_");