[InstrProf] Ignore -Wcast-qual after D153911 to fix build failure (NFC)

/data/llvm-project/compiler-rt/lib/profile/InstrProfilingMerge.c:46:60: error: cast from 'const char *' to 'struct __llvm_profile_header *' drops const qualifier [-Werror,-Wcast-qual]
  __llvm_profile_header *Header = (__llvm_profile_header *)ProfileData;
                                                           ^
/data/llvm-project/compiler-rt/lib/profile/InstrProfilingMerge.c:49:30: error: cast from 'const char *' to 'struct __llvm_profile_data *' drops const qualifier [-Werror,-Wcast-qual]
      (__llvm_profile_data *)(ProfileData + sizeof(__llvm_profile_header) +
                             ^
/data/llvm-project/compiler-rt/lib/profile/InstrProfilingMerge.c:77:41: error: cast from 'const struct __llvm_profile_data *' to 'struct __llvm_profile_data *' drops const qualifier [-Werror,-Wcast-qual]
       DstData = (__llvm_profile_data *)__llvm_profile_begin_data();
                                        ^
/data/llvm-project/compiler-rt/lib/profile/InstrProfilingMerge.c:109:60: error: cast from 'const char *' to 'struct __llvm_profile_header *' drops const qualifier [-Werror,-Wcast-qual]
  __llvm_profile_header *Header = (__llvm_profile_header *)ProfileData;
                                                           ^
/data/llvm-project/compiler-rt/lib/profile/InstrProfilingMerge.c:116:30: error: cast from 'const char *' to 'struct __llvm_profile_data *' drops const qualifier [-Werror,-Wcast-qual]
      (__llvm_profile_data *)(ProfileData + sizeof(__llvm_profile_header) +
                             ^
/data/llvm-project/compiler-rt/lib/profile/InstrProfilingMerge.c:129:40: error: cast from 'const struct __llvm_profile_data *' to 'struct __llvm_profile_data *' drops const qualifier [-Werror,-Wcast-qual]
      DstData = (__llvm_profile_data *)__llvm_profile_begin_data(),
                                       ^
/data/llvm-project/compiler-rt/lib/profile/InstrProfilingMerge.c:179:34: error: cast from 'const char *' to 'struct ValueProfData *' drops const qualifier [-Werror,-Wcast-qual]
    VPMergeHook((ValueProfData *)SrcValueProfData, DstData);
                                 ^
/data/llvm-project/compiler-rt/lib/profile/InstrProfilingMerge.c:181:46: error: cast from 'const char *' to 'struct ValueProfData *' drops const qualifier [-Werror,-Wcast-qual]
        SrcValueProfData + ((ValueProfData *)SrcValueProfData)->TotalSize;
                                             ^
...