introduce a target to build the kernel HermitCore

- the target avoids the usage of SSE & AVX within the kernel

src/librustc_target/spec/hermit_kernel_base.rs

@@ -0,0 +1,26 @@
+use crate::spec::{LldFlavor, LinkArgs, LinkerFlavor, PanicStrategy, TargetOptions};
+use std::default::Default;
+
+pub fn opts() -> TargetOptions {
+    let mut pre_link_args = LinkArgs::new();
+    pre_link_args.insert(LinkerFlavor::Lld(LldFlavor::Ld), vec![
+        "--build-id".to_string(),
+        "--hash-style=gnu".to_string(),
+        "--Bstatic".to_string(),
+    ]);
+
+    TargetOptions {
+        linker: Some("rust-lld".to_owned()),
+        executables: true,
+        has_elf_tls: true,
+        linker_is_gnu: true,
+        pre_link_args,
+        no_default_libraries: true,
+        panic_strategy: PanicStrategy::Abort,
+        position_independent_executables: true,
+        relocation_model: "static".to_string(),
+        target_family: None,
+        tls_model: "initial-exec".to_string(),
+        .. Default::default()
+    }
+}

src/librustc_target/spec/mod.rs

@@ -54,6 +54,7 @@ mod dragonfly_base;
 mod freebsd_base;
 mod haiku_base;
 mod hermit_base;
+mod hermit_kernel_base;
 mod linux_base;
 mod linux_kernel_base;
 mod linux_musl_base;
@@ -481,6 +482,7 @@ supported_targets! {
 
     ("aarch64-unknown-hermit", aarch64_unknown_hermit),
     ("x86_64-unknown-hermit", x86_64_unknown_hermit),
+    ("x86_64-unknown-hermit-kernel", x86_64_unknown_hermit_kernel),
 
     ("riscv32i-unknown-none-elf", riscv32i_unknown_none_elf),
     ("riscv32imc-unknown-none-elf", riscv32imc_unknown_none_elf),

src/librustc_target/spec/x86_64_unknown_hermit_kernel.rs

@@ -0,0 +1,23 @@
+use crate::spec::{LldFlavor, LinkerFlavor, Target, TargetResult};
+
+pub fn target() -> TargetResult {
+    let mut base = super::hermit_kernel_base::opts();
+    base.cpu = "x86-64".to_string();
+    base.max_atomic_width = Some(64);
+    base.features = "-mmx,-sse,-sse2,-sse3,-ssse3,-sse4.1,-sse4.2,-3dnow,-3dnowa,-avx,-avx2,+soft-float".to_string();
+    base.stack_probes = true;
+
+    Ok(Target {
+        llvm_target: "x86_64-unknown-hermit".to_string(),
+        target_endian: "little".to_string(),
+        target_pointer_width: "64".to_string(),
+        target_c_int_width: "32".to_string(),
+        data_layout: "e-m:e-i64:64-f80:128-n8:16:32:64-S128".to_string(),
+        arch: "x86_64".to_string(),
+        target_os: "hermit".to_string(),
+        target_env: String::new(),
+        target_vendor: "unknown".to_string(),
+        linker_flavor: LinkerFlavor::Lld(LldFlavor::Ld),
+        options: base,
+    })
+}