openssh @8.1p1_9+gsskex+kerberos5+xauth build fails on Big Sur

[rswail (Ron Wail)]

Building on Big Sur 11.0.1 Beta 2, Xcode 12.2 Release Candidate

openssh fails to build with the following error during configuration:

  :info:configure configure: error: *** compiler cannot create working executables, check config.log ***
  :info:configure Command failed:  cd "/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_r  elease_tarballs_ports_net_openssh/openssh/work/openssh-8.1p1" && ./configure --prefix=/opt/local --with-ssl-dir=/opt/local --sys  confdir=/opt/local/etc/ssh --with-privsep-path=/var/empty --with-md5-passwords --with-pid-dir=/opt/local/var/run --with-pam --ma  ndir=/opt/local/share/man --with-zlib=/opt/local --with-libedit --with-pie --with-xauth=/opt/local/bin/xauth --without-ldns --wi  th-audit=bsm --with-keychain=apple --with-kerberos5=/opt/local --with-4in6 --disable-utmp --disable-wtmp --with-privsep-user=_ss  hd
  :info:configure Exit code: 1

The config.log (full log attached) has:

  configure:9029: checking compiler and flags for sanity
  configure:9047: /usr/bin/clang -o conftest -pipe -Os -fPIE -isysroot/Applications/Xcode-beta.app/Contents/Developer/Platforms/Ma
  cOSX.platform/Developer/SDKs/MacOSX11.0.sdk -arch x86_64 -pipe -Wunknown-warning-option -Qunused-arguments -Wall -Wpointer-arith
   -Wuninitialized -Wsign-compare -Wformat-security -Wsizeof-pointer-memaccess -Wno-pointer-sign -Wno-unused-result -fno-strict-al
  iasing -mretpoline -D_FORTIFY_SOURCE=2 -ftrapv -fno-builtin-memset -fstack-protector-strong -I/opt/local/include -DBROKEN_STRNVI
  S=1 -D__APPLE_SANDBOX_NAMED_EXTERNAL__ -D__APPLE_API_STRICT_CONFORMANCE -isysroot/Applications/Xcode-beta.app/Contents/Developer
  /Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.0.sdk -L/opt/local/lib -Wl,-headerpad_max_install_names -Wl,-search_paths_fir
  st -Wl,-pie -Wl,-syslibroot,/Applications/Xcode-beta.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.0.
  sdk -arch x86_64 -fstack-protector-strong conftest.c  -framework Security -framework Security >&5
  conftest.c:88:2: error: implicitly declaring library function 'exit' with type 'void (int) __attribute__((noreturn))' [-Werror,-
  Wimplicit-function-declaration]
   exit(0);
   ^
  conftest.c:88:2: note: include the header <stdlib.h> or explicitly provide a declaration for 'exit'
  1 error generated.
  configure:9047: $? = 1
  configure: program exited with status 1

[rswail (Ron Wail)]

Full config.log

[mf2k (Frank Schima)]

Duplicate of #60959.