Bootstrap failed on FreeBSD

[Curculigo]

$ ./bootstrap.sh buildmuon
+ dir=buildmuon
+ mkdir -p buildmuon
+ pkgconf_cmd=''
+ command -v pkgconf
+ pkgconf_cmd=pkgconf
+ [ -n pkgconf ]
+ pkgconf libpkgconf
+ pkgconf_src=libpkgconf.c
+ pkgconf --cflags libpkgconf
+ pkgconf_cflags='-I/usr/local/include/pkgconf -DBOOTSTRAP_HAVE_LIBPKGCONF'
+ pkgconf --libs libpkgconf
+ pkgconf_libs='-L/usr/local/lib -lpkgconf'
+ c99 -Iinclude -I/usr/local/include/pkgconf -DBOOTSTRAP_HAVE_LIBPKGCONF src/amalgam.c -L/usr/local/lib -lpkgconf -o buildmuon/muon
In file included from src/amalgam.c:128:
src/platform/posix/init.c:30:16: error: use of undeclared identifier 'SA_SIGINFO'
   30 |                         .sa_flags = SA_SIGINFO,
      |                                     ^
1 error generated.