Delphi 10.4 Firedac Error 314 on OSX Catalina - macos

Question

How do I correctly provide the libfbclient.dylib for running Firedac/Firebird in OSX to avoid crashing with this message (here in German):
EFDException: [FireDAC][Phys][FB]-314. Laden der Herstellerbibliothek [libfbclient.dylib or libfbembed.dylib] nicht möglich.
To avoid some questions upfront: The software I am compiling already runs fine on Windows and Linux, in OSX it just wouldn't find the libfbclient.dylib. Also all non DB related unit tests run fine on all three platforms. And I made sure that the dylibs have 64 bitness like the executable, I took them from a fresh firebird 3 installation on the same Mac. The project is an application server (Windows service or Linux/OSX daemon).
I create all components dynamically and usually store the fbclient and other required libraries in the a folder together with the executable as I never write things into customers system folders and try to avoid changing things like the system path whenever possible.
const
{$IFDEF MSWINDOWS}
CLIENTNAME = 'fbclient.dll';
{$ENDIF}
{$IFDEF LINUX}
CLIENTNAME = 'libfbclient.so';
{$ENDIF}
{$IFDEF OSX}
CLIENTNAME = 'libfbclient.dylib';
{$ENDIF}
...
fDBLink := TFDPhysFBDriverLink.create(nil);
fDBLink.vendorLib := IncludeTrailingPathDelimiter(extractFilePath(paramstr(0))) + CLIENTNAME;
The Embacadero documentations states the executable searches in the application folder first, so I also tried to omit setting the expicit verndorLib - no difference. I also tried the subfolder Contents/MacOS and the parent folder, also no difference.
As I am not very used to the Unix platform I have no idea if there are system commands that can help finding out why(!) Firedac cannot load the library.
UPDATE 1
Meanwhile I discovered that I instanciated a TFDPhysFBDriverLink Object with every database instance what caused the VendorLib path being detected as empty in FDDriver. After correction the error message contains the complete path to libfbclient.dylib and I verified that it really lives there. I debugged into the Firedac code to where the Library is loaded with LoadLibrary: The path is correct and still it returns 0 in OSX.

Answer 1

Finally I solved it.
The problem remaining after fixing the VendorLib path seems to be the libtommath.dylib dependency. Inspecting libfbclient.dylib with otool -L shows fulfilled depedencies to files living in the standard folders and one special one:
#rpath/lib/libtommath.dylib
To my knowledge rpath default is the path where the executable is living, so I tried this approach:
create a subfolder lib for the dylibs I bundle with my application
deploy libfbclient.dylib and libtommath.dylib in subfolder lib
change TFDPhysFBDriverLink's VendorLib to the new path (including /lib)
This works fine and is a solution easy to implement. In Linux this Problem did not arise as one of my installation dependencies is the libtommath package.