Add -C no-stack-check

Fixes #16980.

src/librustc/driver/config.rs

@@ -390,6 +390,8 @@ cgoptions!(
         "divide crate into N units to optimize in parallel"),
     remark: Passes = (SomePasses(Vec::new()), parse_passes,
         "print remarks for these optimization passes (space separated, or \"all\")"),
+    no_stack_check: bool = (false, parse_bool,
+        "disable checks for stack exhaustion (a memory-safety hazard!)"),
 )
 
 pub fn build_codegen_options(matches: &getopts::Matches) -> CodegenOptions

src/librustc/middle/trans/base.rs

@@ -204,7 +204,7 @@ pub fn decl_fn(ccx: &CrateContext, name: &str, cc: llvm::CallConv,
     // Function addresses in Rust are never significant, allowing functions to be merged.
     llvm::SetUnnamedAddr(llfn, true);
 
-    if ccx.is_split_stack_supported() {
+    if ccx.is_split_stack_supported() && !ccx.sess().opts.cg.no_stack_check {
         set_split_stack(llfn);
     }