Add initial files for aosp_riscv64 target

Add barebones files to support building for a riscv64 target.

Bug: 250918230
Test: lunch aosp_riscv64-userdebug && m ALLOW_MISSING_DEPENDENCIES=true nothing
Change-Id: I61e6ecf6706b7682c77b07e6593d78c7d1eaef39
diff --git a/core/combo/TARGET_linux-riscv64.mk b/core/combo/TARGET_linux-riscv64.mk
new file mode 100644
index 0000000..8f8fd3c
--- /dev/null
+++ b/core/combo/TARGET_linux-riscv64.mk
@@ -0,0 +1,40 @@
+#
+# Copyright (C) 2022 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+# Configuration for Linux on riscv64 as a target.
+# Included by combo/select.mk
+
+# Provide a default variant.
+ifeq ($(strip $(TARGET_ARCH_VARIANT)),)
+TARGET_ARCH_VARIANT := riscv64
+endif
+
+# Include the arch-variant-specific configuration file.
+# Its role is to define various ARCH_X86_HAVE_XXX feature macros,
+# plus initial values for TARGET_GLOBAL_CFLAGS
+#
+TARGET_ARCH_SPECIFIC_MAKEFILE := $(BUILD_COMBOS)/arch/$(TARGET_ARCH)/$(TARGET_ARCH_VARIANT).mk
+ifeq ($(strip $(wildcard $(TARGET_ARCH_SPECIFIC_MAKEFILE))),)
+$(error Unknown $(TARGET_ARCH) architecture version: $(TARGET_ARCH_VARIANT))
+endif
+
+include $(TARGET_ARCH_SPECIFIC_MAKEFILE)
+
+define $(combo_var_prefix)transform-shared-lib-to-toc
+$(call _gen_toc_command_for_elf,$(1),$(2))
+endef
+
+TARGET_LINKER := /system/bin/linker64