compiler: build separation runtime with clite

runtime/internal/clite/bitcast/_cast/cast.c

@@ -0,0 +1,17 @@
+typedef union {
+    double d;
+    float  f;
+    long   v;
+} castUnion;
+
+double llgoToFloat64(long v) {
+    castUnion k;
+    k.v = v;
+    return k.d;
+}
+
+float llgoToFloat32(long v) {
+    castUnion k;
+    k.v = v;
+    return k.f;
+}