I have just updated my Macbook to Monterey and installed XCode 13. I'm now seeing errors when trying to link my code - for example one library needs to link to the system python2.7, but gives the error:

Keiths-MacBook-Pro:libcdb keith$ make rm -f libcdb.1.0.0.dylib
libcdb.dylib libcdb.1.dylib libcdb.1.0.dylib
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang++
-stdlib=libc++ -headerpad_max_install_names  -arch x86_64 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.0.sdk
-mmacosx-version-min=10.13 -Wl,-rpath,@executable_path/../Frameworks -Wl,-rpath,/usr/local/Qt-5.15.7/lib -single_module -dynamiclib -compatibility_version    1.0 -current_version    1.0.0 -install_name libcdb.1.dylib -o libcdb.1.0.0.dylib release/db.o release/KDTree.o release/db_Wlist.o release/db_VSeg.o
release/db_View.o release/db_ViaInst.o release/db_ViaGen.o
release/db_Via.o release/db_Vertex.o release/db_Vector.o
release/db_Utils.o release/db_Trapezoid.o release/db_Transform64.o
release/db_Transform.o release/db_Techfile.o release/db_Style.o
release/db_Signal.o release/db_Shape.o release/db_SegParam.o
release/db_Segment.o release/db_Rectangle.o release/db_Rect.o
release/db_QTree.o release/db_Property.o release/db_Polygon.o
release/db_PointList.o release/db_Point.o release/db_Pin.o
release/db_Path.o release/db_ObjList.o release/db_Obj.o
release/db_Net.o release/db_Mst.o release/db_Mpp.o release/db_Lpp.o
release/db_Line.o release/db_Library.o release/db_Layer.o
release/db_Label.o release/db_InstPin.o release/db_Inst.o
release/db_HVTree.o release/db_HSeg.o release/db_HierObj.o
release/db_Group.o release/db_Ellipse.o release/db_Edge.o
release/db_CellView.o release/db_Cell.o release/db_Array.o
release/db_Arc.o  -F/usr/local/Qt-5.15.7/lib -L../libcpp/release -lcpp
-L/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/config
-lpython2.7 -framework QtWidgets -framework QtGui -framework AppKit -framework Metal -framework QtNetwork -framework QtCore -framework DiskArbitration -framework IOKit -framework OpenGL -framework AGL
ld: cannot link directly with dylib/framework, your binary is not an
allowed client of
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.0.sdk/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/config/libpython2.7.tbd
for architecture x86_64 clang: error: linker command failed with exit
code 1 (use -v to see invocation) make: ***
[release/libcdb.1.0.0.dylib] Error 1

Given that I have recompiled (successfully) the Qt libs and the code for this library, why is it giving me this 'your binary is not an allowed client' error?
As far as I can see the python2.7 paths have not changed, so the error is baffling.
So the quick and diirty fix is to edit the Python.tdb file that is located at:
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.0.sdk/System/Library/Frameworks/Python.framework/Versions/Current/Python.tdb
And add your library/executable targets to the clients list.
Of course, there is a reason Apple are doing this - python2 is deprecated and sooner or later they will drop it. But until they do, this works.
Linking to system python gives 'binary is not an allowed client' error