Gentoo's Bugzilla –
Attachment 855036 Details for
Bug 898174sci-geosciences/gtk-g-rays2-2.05 fails to compile (MUSL-CLANG-SYSTEM): wbt201.c:386:5: error: call to undeclared function setlocale; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]