Bug#921443: ddnet FTBFS on architectures where char is unsigned

[Adrian Bunk]

Source: ddnet
Version: 11.7.2-1
Severity: serious
Tags: ftbfs

https://buildd.debian.org/status/package.php?p=ddnet&suite=sid

...
/usr/bin/c++  -DCONF_AUTOUPDATE -DCONF_OPENSSL -DCONF_SQL -DCONF_WEBSOCKETS -DGLEW_STATIC -D_FORTIFY_SOURCE=2 -I/<<PKGBUILDDIR>>/obj-aarch64-linux-gnu/src -I/<<PKGBUILDDIR>>/src -I/usr/include/mariadb  -g -O2 -fdebug-prefix-map=/<<PKGBUILDDIR>>=. -fstack-protector-strong -Wformat -Werror=format-security -Wall -pedantic -O3 -Wdate-time -D_FORTIFY_SOURCE=2   -fstack-protector-all -Wall -Wextra -Wno-unused-parameter -Wno-missing-field-initializers -Wformat=2 -std=gnu++11 -o CMakeFiles/testrunner.dir/src/test/str.cpp.o -c /<<PKGBUILDDIR>>/src/test/str.cpp
/<<PKGBUILDDIR>>/src/test/str.cpp: In member function 'virtual void Str_Utf8ToLower_Test::TestBody()':
/<<PKGBUILDDIR>>/src/test/str.cpp:70:28: error: narrowing conversion of '-128' from 'int' to 'char' inside { } [-Wnarrowing]
  const char a[2] = {-128, 0};
                            ^
make[5]: *** [CMakeFiles/testrunner.dir/build.make:183: CMakeFiles/testrunner.dir/src/test/str.cpp.o] Error 1