Use musl for biscuit programs in RISC-V

Makefile

@@ -41,7 +41,7 @@ ifneq ($(arch), x86_64)
 endif
 
 biscuit:
-ifeq ($(arch), $(filter $(arch), x86_64 aarch64))
+ifeq ($(arch), $(filter $(arch), x86_64 aarch64 riscv64))
 	@echo Building biscuit programs
 	@mkdir -p biscuit/build
 	@cd biscuit/build && cmake $(cmake_build_args) .. && make

README.md

@@ -22,6 +22,7 @@ $ sudo pacman -Syu musl # archlinux
 $ brew install FileSottile/musl-cross/musl-cross 
 # for ubuntu 16.04, we should build gcc-musl for newest musl-1.1.21
 # please see build-gcc-musl.md
+# for riscv musl toolchain, please install [musl-riscv-toolchain](https://github.com/jiegec/musl-riscv-toolchain)
 ```
 
 ```bash

biscuit/CMakeLists.txt

@@ -35,8 +35,8 @@ elseif (${ARCH} STREQUAL riscv32)
     set(PREFIX              riscv64-unknown-elf-)
     set(CMAKE_C_FLAGS       "-march=rv32imac -mabi=ilp32 -mcmodel=medany")
 elseif (${ARCH} STREQUAL riscv64)
-    set(PREFIX              riscv64-unknown-elf-)
-    set(CMAKE_C_FLAGS       "-march=rv64imac -mabi=lp64 -mcmodel=medany")
+    set(PREFIX              riscv64-linux-musl-)
+    set(CMAKE_C_FLAGS       "-march=rv64imafdc -mabi=lp64d -mcmodel=medany")
 elseif (${ARCH} STREQUAL aarch64)
     set(PREFIX              aarch64-linux-musl-)
 else ()
@@ -54,8 +54,10 @@ if (KERNEL_HEADERS_DIR)
 	include_directories(${KERNEL_HEADERS_DIR}/include/uapi)
 endif ()
 
-# Execuatble
+# Executable
 foreach (PATH ${SRCS})
+	if (NOT ${ARCH} STREQUAL riscv64 OR NOT "${PATH}" MATCHES "^c/(usertests).c$")
 		get_filename_component(NAME ${PATH} NAME_WE)
 		add_executable(${NAME} ${PATH})
+	endif ()
 endforeach ()