Configure with tcc fails on S3_0+. The reason is that those branches use AC_C_VARARRAYS(), while older branches used custom macro of our own (AC_C_VARARRAYS() wasn't available at the time it was introduced). AC_C_VARARRAYS() is a more complete check for vararrays support than our custom macro was. Needlessly so, as our own macro checked the constructs we actually need.
Configure with tcc fails on S3_0+. The reason is that those branches use AC_C_VARARRAYS(), while older branches used custom macro of our own (AC_C_VARARRAYS() wasn't available at the time it was introduced). AC_C_VARARRAYS() is a more complete check for vararrays support than our custom macro was. Needlessly so, as our own macro checked the constructs we actually need.
We should probably reintroduce our own macro.
As part of #43200, this has also been posted to http://forum.freeciv.org/f/viewtopic.php?f=14&t=92091