msquichelper.h: suppress GCC stringop-overflow warning

[jwhited]

Updates #3918

Description

Builds fail on Linux with more recent versions of GCC (12/13) due to:

/home/jwhited/msquic/src/inc/msquichelper.h:268:28: error: writing 16 bytes into a region of size 0 [-Werror=stringop-overflow=]
  268 |         HexString[i*2 + 1] = HEX_TO_CHAR(Buffer[i] & 0xf);

This PR suppresses that warning as it is likely a false positive.

Testing

N/A

Documentation

N/A

[nibanks]

/Users/runner/work/msquic/msquic/src/inc/msquichelper.h:269:32: error: unknown warning group '-Wstringop-overflow', ignored [-Werror,-Wunknown-warning-option]
#pragma GCC diagnostic ignored "-Wstringop-overflow"
                               ^

[codecov]

Codecov Report

Merging #3949 (8ae642b) into main (136b175) will decrease coverage by 0.28%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #3949      +/-   ##
==========================================
- Coverage   86.69%   86.42%   -0.28%     
==========================================
  Files          56       56              
  Lines       16901    16901              
==========================================
- Hits        14653    14607      -46     
- Misses       2248     2294      +46     

see 11 files with indirect coverage changes