[PATCH v4 2/2] kvm-unit-tests: invoke $LD explicitly

[Dan Cross <cross@oxidecomputer.com>]

Change x86/Makefile.common to invoke the linker directly instead
of using the C compiler as a linker driver.  Plumb LDFLAGS through
to the linker.

This supports building on illumos, allowing the user to use
gold instead of the Solaris linker.  Tested on Linux and illumos.

Signed-off-by: Dan Cross <cross@oxidecomputer.com>
---
 x86/Makefile.common | 9 +++++----
 x86/Makefile.i386   | 1 +
 x86/Makefile.x86_64 | 2 ++
 3 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/x86/Makefile.common b/x86/Makefile.common
index b903988..a600c72 100644
--- a/x86/Makefile.common
+++ b/x86/Makefile.common
@@ -30,7 +30,7 @@ endif
 
 OBJDIRS += lib/x86
 
-$(libcflat): LDFLAGS += -nostdlib
+$(libcflat): LDFLAGS += -nostdlib $(arch_LDFLAGS)
 $(libcflat): CFLAGS += -ffreestanding -I $(SRCDIR)/lib -I lib
 
 COMMON_CFLAGS += -m$(bits)
@@ -61,8 +61,9 @@ else
 # We want to keep intermediate file: %.elf and %.o
 .PRECIOUS: %.elf %.o
 
+%.elf: LDFLAGS = -nostdlib $(arch_LDFLAGS)
 %.elf: %.o $(FLATLIBS) $(SRCDIR)/x86/flat.lds $(cstart.o)
-	$(CC) $(CFLAGS) -nostdlib -o $@ -Wl,-T,$(SRCDIR)/x86/flat.lds \
+	$(LD) $(LDFLAGS) -T $(SRCDIR)/x86/flat.lds -o $@ \
 		$(filter %.o, $^) $(FLATLIBS)
 	@chmod a-x $@
 
@@ -98,8 +99,8 @@ test_cases: $(tests-common) $(tests)
 $(TEST_DIR)/%.o: CFLAGS += -std=gnu99 -ffreestanding -I $(SRCDIR)/lib -I $(SRCDIR)/lib/x86 -I lib
 
 $(TEST_DIR)/realmode.elf: $(TEST_DIR)/realmode.o
-	$(CC) -m32 -nostdlib -o $@ -Wl,-m,elf_i386 \
-	      -Wl,-T,$(SRCDIR)/$(TEST_DIR)/realmode.lds $^
+	$(LD) -m elf_i386 -nostdlib -o $@ \
+	      -T $(SRCDIR)/$(TEST_DIR)/realmode.lds $^
 
 $(TEST_DIR)/realmode.o: bits = $(if $(call cc-option,-m16,""),16,32)
 
diff --git a/x86/Makefile.i386 b/x86/Makefile.i386
index 7d19d55..0a845e6 100644
--- a/x86/Makefile.i386
+++ b/x86/Makefile.i386
@@ -4,6 +4,7 @@ ldarch = elf32-i386
 exe = flat
 bin = elf
 COMMON_CFLAGS += -mno-sse -mno-sse2
+arch_LDFLAGS = -m elf_i386
 
 cflatobjs += lib/x86/setjmp32.o lib/ldiv32.o
 
diff --git a/x86/Makefile.x86_64 b/x86/Makefile.x86_64
index f18c1e2..e19284a 100644
--- a/x86/Makefile.x86_64
+++ b/x86/Makefile.x86_64
@@ -6,9 +6,11 @@ exe = efi
 bin = so
 FORMAT = efi-app-x86_64
 cstart.o = $(TEST_DIR)/efi/efistart64.o
+arch_LDFLAGS = ''
 else
 exe = flat
 bin = elf
+arch_LDFLAGS = -m elf_x86_64
 endif
 
 fcf_protection_full := $(call cc-option, -fcf-protection=full,)
-- 
2.36.1