omni: Use $(HOST_PREBUILT_TAG) where possible

Change-Id: If211d23ce72b3404368cd723cbb9ea801e61802c
diff --git a/build/tasks/cookies.mk b/build/tasks/cookies.mk
index 6c5099a..f2ca0a5 100644
--- a/build/tasks/cookies.mk
+++ b/build/tasks/cookies.mk
@@ -1,7 +1,7 @@
 
 OMNI_TARGET_PACKAGE := $(PRODUCT_OUT)/omni-$(ROM_VERSION).zip
 
-MD5 := prebuilts/build-tools/path/$(HOST_OS)-x86/md5sum
+MD5 := prebuilts/build-tools/path/$(HOST_PREBUILT_TAG)/md5sum
 
 .PHONY: cookies
 cookies: $(INTERNAL_OTA_PACKAGE_TARGET)
diff --git a/build/tasks/kernel.mk b/build/tasks/kernel.mk
index a2c471b..eafaa9f 100644
--- a/build/tasks/kernel.mk
+++ b/build/tasks/kernel.mk
@@ -185,7 +185,7 @@
         # Use the default version of clang if TARGET_KERNEL_CLANG_VERSION hasn't been set by the device config
         KERNEL_CLANG_VERSION := $(LLVM_PREBUILTS_VERSION)
     endif
-    TARGET_KERNEL_CLANG_PATH ?= $(BUILD_TOP)/prebuilts/clang/host/$(HOST_OS)-x86/$(KERNEL_CLANG_VERSION)
+    TARGET_KERNEL_CLANG_PATH ?= $(BUILD_TOP)/prebuilts/clang/host/$(HOST_PREBUILT_TAG)/$(KERNEL_CLANG_VERSION)
     ifeq ($(KERNEL_ARCH),arm64)
         KERNEL_CLANG_TRIPLE ?= CLANG_TRIPLE=aarch64-linux-gnu-
     else ifeq ($(KERNEL_ARCH),arm)