Do not override the deployment target that MacPorts sets.
https://github.com/microsoft/msphpsql/commit/f59f0bcce7d0d000900c820ad4bc1917b3a20dd8
--- config.m4.orig	2018-07-20 02:58:46.000000000 -0500
+++ config.m4	2022-02-03 03:47:07.000000000 -0600
@@ -56,7 +56,6 @@
   HOST_OS_ARCH=`uname`
   if test "${HOST_OS_ARCH}" = "Darwin"; then
       SQLSRV_SHARED_LIBADD="$SQLSRV_SHARED_LIBADD -Wl,-bind_at_load"
-      MACOSX_DEPLOYMENT_TARGET=`sw_vers -productVersion`
   else
       SQLSRV_SHARED_LIBADD="$SQLSRV_SHARED_LIBADD -Wl,-z,now"
   fi