Add hexagon implementations for compiler_rt builtins

Author: androm3da

lib/compiler_rt.zig

@@ -220,6 +220,7 @@ comptime {
     _ = @import("compiler_rt/aulldiv.zig");
     _ = @import("compiler_rt/aullrem.zig");
     _ = @import("compiler_rt/clear_cache.zig");
+    _ = @import("compiler_rt/hexagon.zig");
 
     if (@import("builtin").object_format != .c) {
         _ = @import("compiler_rt/atomics.zig");