add support for linux_riscv64 and freestanding_riscv64

core/sys/info/cpu_riscv64.odin

@@ -0,0 +1,16 @@
+package sysinfo
+
+CPU_Feature :: enum u64 {
+	I = 'I' - 'A', // Base features, don't think this is ever not here.
+	M = 'M' - 'A', // Integer multiplication and division, currently required by Odin.
+	A = 'A' - 'A', // Atomics.
+	F = 'F' - 'A', // Single precision floating point, currently required by Odin.
+	D = 'D' - 'A', // Double precision floating point, currently required by Odin.
+	C = 'C' - 'A', // Compressed instructions.
+	V = 'V' - 'A', // Vector operations.
+}
+
+CPU_Features :: distinct bit_set[CPU_Feature; u64]
+
+cpu_features: Maybe(CPU_Features)
+cpu_name: Maybe(string)