Target stack-probe support configurable finely

This adds capability to configure the target's stack probe support in a
more precise manner than just on/off. In particular now we allow
choosing between always inline-asm, always call or either one of those
depending on the LLVM version on a per-target basis.

compiler/rustc_target/src/spec/linux_kernel_base.rs

@@ -1,4 +1,6 @@
-use crate::spec::{LinkArgs, LinkerFlavor, PanicStrategy, RelocModel, RelroLevel, TargetOptions};
+use crate::spec::{
+    LinkArgs, LinkerFlavor, PanicStrategy, RelocModel, RelroLevel, StackProbeType, TargetOptions,
+};
 
 pub fn opts() -> TargetOptions {
     let mut pre_link_args = LinkArgs::new();
@@ -11,7 +13,7 @@ pub fn opts() -> TargetOptions {
         env: "gnu".to_string(),
         disable_redzone: true,
         panic_strategy: PanicStrategy::Abort,
-        stack_probes: true,
+        stack_probes: StackProbeType::InlineOrCall { min_llvm_version_for_inline: (11, 0, 1) },
         eliminate_frame_pointer: false,
         linker_is_gnu: true,
         position_independent_executables: true,