Build kvm-unit-tests out of tree

It is possible to build kvm-unit-tests out-of-tree by running
`configure` from the destination. Makefiles are created there and
correctly compile.

Switch kvm-unit-tests to build OOT to align with other projects in
out repo. With this, all generated files are in out/.

Change-Id: I324716c663097f2a016a97782df4749975d1c293
diff --git a/Makefile b/Makefile
index 30dbb42..d5cc3e8 100644
--- a/Makefile
+++ b/Makefile
@@ -120,15 +120,19 @@
 
 .PHONY: kvmunittests
 kvmunittests:
-	cd $(KUT_SRC) && \
-		./configure --prefix=$(KUT_OUT) --arch=$(KUT_ARCH) \
+	mkdir -p $(KUT_OUT)
+	cd $(KUT_OUT) && \
+		$(KUT_SRC)/configure \
+			--erratatxt=$(KUT_SRC)/errata.txt \
+			--prefix=$(KUT_OUT) --arch=$(KUT_ARCH) \
 			--cc=$(KUT_CC) --ld=$(KUT_LD) \
 			--objcopy=$(KUT_OBJCOPY) --objdump=$(KUT_OBJDUMP)
-	PATH=$(KUT_PATH) COMMON_CFLAGS=$(KUT_COMMON_CFLAGS) $(MAKE) -C $(KUT_SRC) install
+	PATH=$(KUT_PATH) COMMON_CFLAGS=$(KUT_COMMON_CFLAGS) \
+		$(MAKE) -C $(KUT_OUT) install
 
 .PHONY: kvmunittests_clean
 kvmunittests_clean:
-	- $(MAKE) -C $(KUT_SRC) clean
+	- $(MAKE) -C $(KUT_OUT) clean
 
 
 ##