=> Bootstrap dependency digest>=20010302: found digest-20190127
=> Checksum SHA1 OK for libsigc++-3.0.3.tar.xz
=> Checksum RMD160 OK for libsigc++-3.0.3.tar.xz
=> Checksum SHA512 OK for libsigc++-3.0.3.tar.xz
===> Installing dependencies for libsigc++3-3.0.3
=> Tool dependency libtool-base>=2.4.2nb9: found libtool-base-2.4.6nb2
=> Tool dependency bsdtar-[0-9]*: found bsdtar-3.4.3
=> Tool dependency m4>=1.4: found m4-1.4.18nb2
=> Tool dependency gmake>=3.81: found gmake-4.2.1nb1
=> Tool dependency perl>=5.0: found perl-5.30.3
=> Tool dependency checkperms>=1.1: found checkperms-1.12
=> Build dependency mm-common>=0.9.10: found mm-common-1.0.0
=> Build dependency cwrappers>=20150314: found cwrappers-20180325
===> Skipping vulnerability checks.
WARNING: No /var/db/pkg/pkg-vulnerabilities file found.
WARNING: To fix run: `/usr/sbin/pkg_admin -K /var/db/pkg fetch-pkg-vulnerabilities'.
===> Overriding tools for libsigc++3-3.0.3
===> Extracting for libsigc++3-3.0.3
===> Patching for libsigc++3-3.0.3
===> Creating toolchain wrappers for libsigc++3-3.0.3
===> Configuring for libsigc++3-3.0.3
=> Modifying GNU configure scripts to avoid --recheck
=> Replacing config-guess with pkgsrc versions
=> Replacing config-sub with pkgsrc versions
=> Replacing install-sh with pkgsrc version
=> Adding run-time search paths to pkg-config files.
=> Checking for portability problems in extracted files
checking for a BSD-compatible install... /usr/bin/install -c -o pbulk -g users
checking whether build environment is sane... yes
checking for a thread-safe mkdir -p... build/install-sh -c -d
checking for gawk... /usr/bin/awk
checking whether make sets $(MAKE)... yes
checking whether make supports nested variables... yes
checking whether UID '100' is supported by ustar format... yes
checking whether GID '100' is supported by ustar format... yes
checking how to create a ustar tar archive... plaintar
checking whether make supports nested variables... (cached) yes
checking whether to enable maintainer-specific portions of Makefiles... no
checking whether make supports GNU make features... yes
checking whether the C++ compiler works... yes
checking for C++ compiler default output file name... a.out
checking for suffix of executables... 
checking whether we are cross compiling... no
checking for suffix of object files... o
checking whether we are using the GNU C++ compiler... yes
checking whether c++ accepts -g... yes
checking whether make supports the include directive... yes (GNU style)
checking dependency style of c++... gcc3
checking whether c++ supports C++17 features with -std=c++17... no
checking whether c++ supports C++17 features with +std=c++17... no
checking whether c++ supports C++17 features with -h std=c++17... no
checking whether c++ supports C++17 features with -std=c++1z... no
checking whether c++ supports C++17 features with +std=c++1z... no
checking whether c++ supports C++17 features with -h std=c++1z... no
configure: error: *** A compiler with support for C++17 language features is required.
*** Error code 1

Stop.
make[1]: stopped in /tree/pkgsrc/devel/libsigc++3
*** Error code 1

Stop.
make: stopped in /tree/pkgsrc/devel/libsigc++3