[libc][NFC] Clean up stray ';' and default enum warning

Summary:
Cleans up two warnings I get locally while building.

Author: jhuber6

libc/test/src/__support/FPUtil/fpbits_test.cpp

@@ -237,8 +237,6 @@ template <typename T> constexpr auto make(Sign sign, FP fp) {
     return T::signaling_nan(sign);
   case FP::QUIET_NAN:
     return T::quiet_nan(sign);
-  default:
-    __builtin_unreachable();
   }
 }
 

libc/utils/gpu/loader/Loader.h

@@ -85,7 +85,7 @@ void *copy_argument_vector(int argc, char **argv, Allocator alloc) {
   // Ensure the vector is null terminated.
   reinterpret_cast<void **>(dev_argv)[argv_size] = nullptr;
   return dev_argv;
-};
+}
 
 /// Copy the system's environment to GPU memory allocated using \p alloc.
 template <typename Allocator>
@@ -95,7 +95,7 @@ void *copy_environment(char **envp, Allocator alloc) {
     ++envc;
 
   return copy_argument_vector(envc, envp, alloc);
-};
+}
 
 inline void handle_error(const char *msg) {
   fprintf(stderr, "%s\n", msg);