Bug#879071: 0ad FTBFS with on armhf with gcc 7: error: call of overloaded 'abs(unsigned int)' is ambiguous

[Adrian Bunk]

Source: 0ad
Version: 0.0.21-2
Severity: serious
Tags: buster sid

https://tests.reproducible-builds.org/debian/rb-pkg/unstable/armhf/0ad.html
https://buildd.debian.org/status/fetch.php?pkg=0ad&arch=armhf&ver=0.0.22-1&stamp=1508365643&raw=0

...
../../../source/gui/CDropDown.cpp: In member function 'virtual InReaction CDropDown::ManuallyHandleEvent(const SDL_Event_*)':
../../../source/gui/CDropDown.cpp:355:94: error: call of overloaded 'abs(unsigned int)' is ambiguous
       diff = std::abs(pList->m_Items[i].GetRawString().LowerCase()[j] - (int)m_InputBuffer[j]);
                                                                                              ^
In file included from /usr/include/c++/7/cmath:47:0,
                 from /usr/include/c++/7/math.h:36,
                 from ../../../source/lib/posix/posix_types.h:48,
                 from ../../../source/lib/precompiled.h:64,
                 from ../../../source/pch/gui/precompiled.h:18:
/usr/include/c++/7/bits/std_abs.h:78:3: note: candidate: constexpr long double std::abs(long double)
   abs(long double __x)
   ^~~
/usr/include/c++/7/bits/std_abs.h:74:3: note: candidate: constexpr float std::abs(float)
   abs(float __x)
   ^~~
/usr/include/c++/7/bits/std_abs.h:70:3: note: candidate: constexpr double std::abs(double)
   abs(double __x)
   ^~~
/usr/include/c++/7/bits/std_abs.h:61:3: note: candidate: long long int std::abs(long long int)
   abs(long long __x) { return __builtin_llabs (__x); }
   ^~~
/usr/include/c++/7/bits/std_abs.h:56:3: note: candidate: long int std::abs(long int)
   abs(long __i) { return __builtin_labs(__i); }
   ^~~
In file included from /usr/include/c++/7/bits/std_abs.h:38:0,
                 from /usr/include/c++/7/cmath:47,
                 from /usr/include/c++/7/math.h:36,
                 from ../../../source/lib/posix/posix_types.h:48,
                 from ../../../source/lib/precompiled.h:64,
                 from ../../../source/pch/gui/precompiled.h:18:
/usr/include/stdlib.h:735:12: note: candidate: int abs(int)
 extern int abs (int __x) __THROW __attribute__ ((__const__)) __wur;
            ^~~
gui.make:198: recipe for target 'obj/gui_Release/CDropDown.o' failed
make[3]: *** [obj/gui_Release/CDropDown.o] Error 1