webkitgtk2-2.4.9: no rebuild possible with gcc 5.5 upto gcc 9.2

[wwwutz]

TLDR: you must update

Source/WebKit2/Shared/API/c/WKString.cpp: In function 'size_t WKStringGetCharacters(WKStringRef, WKChar*, size_t)':
Source/WebKit2/Shared/API/c/WKString.cpp:58:72: error: invalid static_cast from type 'WKChar*' {aka 'short unsigned int*'} to type 'UChar*' {aka 'char16_t*'}
   58 |     return (toImpl(stringRef)->getCharacters(static_cast<UChar*>(buffer), bufferLength));
      |                                                                        ^

[wwwutz]

fixed by #1257