Don't look for old RUSTC_DEBUGINFO vars (#313)

Author: tmandry

crates/backtrace-sys/build.rs

@@ -89,14 +89,6 @@ fn main() {
     build.define("_GNU_SOURCE", "1");
     build.define("_LARGE_FILES", "1");
 
-    // When we're built as part of the Rust compiler, this is used to enable
-    // debug information in libbacktrace itself.
-    if cfg!(feature = "rustc-dep-of-std") {
-        let any_debug = env::var("RUSTC_DEBUGINFO").unwrap_or_default() == "true"
-            || env::var("RUSTC_DEBUGINFO_LINES").unwrap_or_default() == "true";
-        build.debug(any_debug);
-    }
-
     let syms = [
         "backtrace_full",
         "backtrace_dwarf_add",