autoreconf fails and it's a trivial fix to the generated configure, so let's just patch that instead. This is fixed in autoconf itself in newer versions. https://bugs.gentoo.org/879689 --- a/configure +++ b/configure @@ -6289,6 +6289,7 @@ cat confdefs.h >>conftest.$ac_ext cat >>conftest.$ac_ext <<_ACEOF /* end confdefs.h. */ #include +#include #if ((' ' & 0x0FF) == 0x020) # define ISLOWER(c) ('a' <= (c) && (c) <= 'z') # define TOUPPER(c) (ISLOWER(c) ? 'A' + ((c) - 'a') : (c))