cmake: Update the RISCV build to work with GCC 8.2.0

CMakeLists.txt

@@ -72,11 +72,11 @@ if(KernelArchARM)
 endif()
 if(KernelArchRiscV)
     if(Kernel64)
-        string(APPEND c_common_flags " -march=rv64imac")
-        string(APPEND c_common_flags " -mabi=lp64")
+        string(APPEND common_flags " -march=rv64imac")
+        string(APPEND common_flags " -mabi=lp64")
     else()
-        string(APPEND c_common_flags " -march=rv32ima")
-        string(APPEND c_common_flags " -mabi=ilp32")
+        string(APPEND common_flags " -march=rv32imac")
+        string(APPEND common_flags " -mabi=ilp32")
     endif()
 endif()
 string(APPEND common_flags " ${build_arch}")

gcc.cmake

@@ -30,10 +30,8 @@ if("${CROSS_COMPILER_PREFIX}" STREQUAL "")
         set(CROSS_COMPILER_PREFIX "arm-linux-gnueabihf-" CACHE INTERNAL "")
     elseif(AARCH64)
         set(CROSS_COMPILER_PREFIX "aarch64-linux-gnu-" CACHE INTERNAL "")
-    elseif(RISCV32)
-        set(CROSS_COMPILER_PREFIX "riscv32-unknown-elf-" CACHE INTERNAL "")
-    elseif(RISCV64)
-        set(CROSS_COMPILER_PREFIX "riscv64-unknown-elf-" CACHE INTERNAL "")
+    elseif(RISCV32 OR RISCV64)
+        set(CROSS_COMPILER_PREFIX "riscv64-unknown-linux-gnu-" CACHE INTERNAL "")
     else()
         # If we haven't set a target above we assume x86_64/ia32 target
         if(APPLE)