internal/build:compile with c mode,when c file

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

@@ -0,0 +1,35 @@
+typedef union
+{
+    double d;
+    float f;
+    long v;
+    long long ll;
+} castUnion;
+
+double llgoToFloat64(long long v)
+{
+    castUnion k;
+    k.ll = v;
+    return k.d;
+}
+
+float llgoToFloat32(int v)
+{
+    castUnion k;
+    k.v = v;
+    return k.f;
+}
+
+long long llgoFromFloat64(double v)
+{
+    castUnion k;
+    k.d = v;
+    return k.ll;
+}
+
+int llgoFromFloat32(float v)
+{
+    castUnion k;
+    k.f = v;
+    return k.v;
+}