These build errors do not occur in the development version. The next release will build, with transfig enabled, on your system.
Should be fixed with commit [4221b5].
Enable compiling transfig with option -std=c23
ps: Correctly encode text marked as TeX text, #203
Provide an updated fig file header for tests
Silence a compiler warning: -Wdiscarded-qualifiers
pict2e, tikz outputs: respect the -O option
Interpret octal escapes as latin 1 encoded