targets: minimal uefi target support (#5452)

* runtime: split baremetal memory setup

* runtime: extract Windows PE globals scan helper

* compileopts,builder: add target linker flavor override

* machine,runtime,targets: add minimal uefi-amd64 target

* runtime,examples: add clean UEFI exit path test

* machine,x86: fix amd64 ABI stack handling

* machine/uefi: add CHAR16 conversion helpers

* machine/uefi: add loaded image protocol support

* runtime: add UEFI PE globals support

* machine,runtime,x86: add UEFI time and text output support

* machine,runtime,x86: add UEFI text and time support

* machine,runtime,examples: add UEFI text input support

* machine,examples: add UEFI graphics output support

* add rest of STOP methods (direct UEFI ABI only)

* runtime: fix UEFI sleep tick conversion

* machine/uefi: make text input waits cooperative

* address TestClangAttributes/uefi-amd64 failure

* address TestConfigLinkerFlavor bug

* uefi: move raw bindings to device package

* strip down implementation to bare minimum

* amd64: rename x86 package

* do git restore upstream/dev for src/net

* add smoketest for uefi-amd64; add required zeroSizeAllocPtr constant

* address PR issues: remove unused files; make putchar() insert '\r' before '\n'

* swap lines around

targets/uefi-amd64.json

@@ -0,0 +1,41 @@
+{
+  "build-tags": ["uefi", "baremetal", "linux", "amd64"],
+  "llvm-target": "x86_64-unknown-windows-gnu",
+  "cpu": "x86-64",
+  "features": "+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87",
+  "goos": "linux",
+  "goarch": "amd64",
+  "gc": "leaking",
+  "scheduler": "none",
+  "linker": "ld.lld",
+  "linker-flavor": "coff",
+  "libc": "picolibc",
+  "automatic-stack-size": false,
+  "default-stack-size": 65536,
+  "cflags": [
+    "-Werror",
+    "-fshort-enums",
+    "-fomit-frame-pointer",
+    "-fno-exceptions", "-fno-unwind-tables", "-fno-asynchronous-unwind-tables",
+    "-ffunction-sections", "-fdata-sections",
+    "-ffreestanding",
+    "-fshort-wchar",
+    "-mno-red-zone"
+  ],
+  "ldflags": [
+    "-m", "i386pep",
+    "--image-base", "0x400000",
+    "--entry", "efi_main",
+    "--subsystem", "efi_application",
+    "-Bdynamic",
+    "--gc-sections",
+    "--no-insert-timestamp",
+    "--no-dynamicbase"
+  ],
+  "extra-files": [
+    "src/device/amd64/cpu_amd64.S",
+    "src/device/uefi/asm_amd64.S",
+    "src/runtime/asm_amd64_windows.S"
+  ],
+  "gdb": ["gdb-multiarch", "gdb"]
+}