With autoconf-2.71 and gcc-13.2.1 build fails like this:

gcc -DHAVE_CONFIG_H -DLOCALEDIR=\"/usr/local/share/locale\" -I. -I..  -I. -I. -I../intl   -Wall -W -Wredundant-decls -Wshadow -Wstrict-prototypes -Wmissing-prototypes -Wnested-externs -Wmissing-declarations -Wcomment -Wbad-function-cast -Wcast-align  -g -O0 -fsanitize=address -MT indent.o -MD -MP -MF .deps/indent.Tpo -c -o indent.o indent.c
indent.c: In function ‘main’:
indent.c:1063:5: error: implicit declaration of function ‘setlocale’
 1063 |     setlocale(LC_ALL, "");
      |     ^~~~~~~~~

This is bacause a use of setlocale() and an inclusion of locale.h, which declares setlocale() are guarded with a different macro.

A fix is attached.