tools: Enable Rust sim builds on Intel Macs

Add support for building Rust apps on the NuttX simulator running on
Intel (x86_64) macOS.

- Add tools/x86_64-unknown-nuttx-macho.json, a Mach-O Rust target for
  the macOS sim.
- Rust.defs: select the new x86_64 macho target for sim on macOS.
- boards/sim/.../Make.defs: keep the default PIC/PIE-compatible code
  generation on macOS by not adding -fno-pic/-mcmodel=medium.
- sethost.sh: enable CONFIG_HOST_X86_64 for non-arm64 hosts.

Signed-off-by: Shoji Tokunaga <toku@mac.com>

tools/Rust.defs

@@ -46,6 +46,8 @@ ifeq ($(CONFIG_ARCH_SIM),y)
   else ifeq ($(CONFIG_HOST_MACOS),y)
     ifeq ($(LLVM_ARCHTYPE),aarch64)
       RUSTFLAGS += --target $(TOPDIR)/tools/aarch64-unknown-nuttx-macho.json
+    else ifeq ($(LLVM_ARCHTYPE),x86_64)
+      RUSTFLAGS += --target $(TOPDIR)/tools/x86_64-unknown-nuttx-macho.json
     else
       $(error Unsupported Rust SIM target on macOS: LLVM_ARCHTYPE=$(LLVM_ARCHTYPE))
     endif

tools/aarch64-unknown-nuttx-macho.json

@@ -23,6 +23,7 @@
   },
   "os": "nuttx",
   "panic-strategy": "abort",
+  "relocation-model": "pic",
   "split-debuginfo": "off",
   "stack-probes": {
     "kind": "inline"

tools/sethost.sh

@@ -191,6 +191,9 @@ if [ "X$host" == "Xlinux" -o "X$host" == "Xmacos" -o "X$host" == "Xbsd" ]; then
     if [ "X$cpu" == "Xarm64" ]; then
       echo "  Select CONFIG_HOST_ARM64=y"
       kconfig-tweak --file $nuttx/.config --enable CONFIG_HOST_ARM64
+    else
+      echo "  Select CONFIG_HOST_X86_64=y"
+      kconfig-tweak --file $nuttx/.config --enable CONFIG_HOST_X86_64
     fi
   fi
 

tools/x86_64-unknown-nuttx-macho.json

@@ -0,0 +1,36 @@
+{
+  "arch": "x86_64",
+  "archive-format": "darwin",
+  "binary-format": "mach-o",
+  "cpu": "x86-64",
+  "crt-objects-fallback": "false",
+  "data-layout": "e-m:o-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128",
+  "debuginfo-kind": "dwarf",
+  "default-uwtable": true,
+  "disable-redzone": true,
+  "emit-debug-gdb-scripts": false,
+  "frame-pointer": "always",
+  "function-sections": false,
+  "linker-flavor": "gnu-lld",
+  "lld-flavor": "darwin",
+  "llvm-target": "x86_64-apple-macosx",
+  "max-atomic-width": 64,
+  "metadata": {
+    "description": "x86_64 Mach-O target for NuttX sim on macOS",
+    "host_tools": false,
+    "std": true,
+    "tier": 3
+  },
+  "os": "nuttx",
+  "panic-strategy": "abort",
+  "relocation-model": "pic",
+  "split-debuginfo": "off",
+  "stack-probes": {
+    "kind": "inline"
+  },
+  "target-family": [
+    "unix"
+  ],
+  "target-pointer-width": 64,
+  "vendor": "unknown"
+}