EFI: Initial test EFI application

* Only set HAIKU_BOOT_PLATFORM to bios_ia32 if not defined
* Add gnuefi build feature
* Introduce BOOT_LDFLAGS, and move options for passing to linker
  into ArchitectureSetup
* x86_64 compile fixes for warnings in boot loader
* loader/elf.cpp: don't include ELF32 support when targeting EFI
* relocation_func.cpp: copy of the relocation code from gnuefi
  to make _relocate extern "C", and avoid including <efilib.h>
* boot_loader_efi.ld: copy of gnuefi's elf_x86_64_efi.lds,
  modified to include support for C++ constructors, etc. Keep in
  sync with the gnuefi package

Signed-off-by: Jessica Hamilton <[email protected]>

build/jam/BuildFeatures

@@ -571,6 +571,23 @@ if [ IsPackageAvailable expat_devel ] {
 }
 
 
+# gnu-efi
+if $(TARGET_PACKAGING_ARCH) = x86_64 {
+	if [ IsPackageAvailable gnuefi ] {
+		ExtractBuildFeatureArchives gnuefi :
+			file: base gnuefi
+				headers: $(developHeadersDir)/gnuefi
+				headersProtocol: $(developHeadersDir)/gnuefi/protocol
+				headersArch: $(developHeadersDir)/gnuefi/$(TARGET_ARCH)
+				libdir: $(libDir)/gnuefi
+			;
+
+		EnableBuildFeatures gnuefi ;
+	} else {
+		Echo "gnuefi support not available on $(TARGET_PACKAGING_ARCH)" ;
+	}
+}
+
 # GPL add-ons
 if $(HAIKU_INCLUDE_GPL_ADDONS) = 1 {
 	EnableBuildFeatures gpl ;