Details in https://github.com/johnhcc/homebrew-gs-x11/issues/1

macOS 11.2.3 (x86), zsh, en_US.UTF-8

See the gv_user.ad rule in src/Makefile{.in,.am}

Building GV.ad in src/Makefile inserts a handful of copyright lines. The copyright line for José Marchesi has the é encoded in Latin-1 (0xE9). This trips up macOS (BSD) sed with a Unicode/UTF-8 locale when building GV:

sed: RE error: illegal byte sequence

IIRC one other file contains a UTF-8 encoded equivalent. All other copyright lines for José use an ASCII 'e'.

The top-level configure script sets LC_ALL=C, but this does not propagate to the Makefiles:

# NLS nuisances.
LC_ALL=C
export LC_ALL
LANGUAGE=C
export LANGUAGE

Adding LC_ALL=C to the make line overrides the issue and the build succeeds:

make install LC_ALL=C

Gnu sed doesn't seem to care about the encoding. Those building on macOS would need to install and understand how to override the build environment to use Gnu sed.

Possible fixes:

1. Clean up binary characters in this build chain.
2. Change configure to insert LANG/LC_ALL=C in the Makefile.
3. Add LC_ALL=C to src/Makefile.{in,am}