To use gdb with Haiku apps you need it to talk our custom debug protocol which is not what GDB uses on other platforms. If you don’t include these patches, you get a GDB that runs fine, but cannot be used on native applications, only for remote debugging (you can use the “target remote” command and connect to a linux machine and debug programs running there for example). So, it runs, but it’s completely useless for the main case you’d use it.
These patches were never updated to newer versions of gdb.
No, there is no magic with path involved in selecting the standard library to use. It looks like something in the freepascal toolchain is using the wrong linker (compiling with gcc-x86 and linking with old ld instead of ld-x86) or explicitly linking that library when it shouldn’t.
This has been the main problem with freepascal for years. It builds and runs fine when compiled with gcc2, but then it gets very confused when you try to link some libraries against gcc8. So we should make sure that all of freepascal is built with gcc8, and is correctly set up to pick libraries in the correct directories to make sure it always stays in the gcc8 world and does not pick some things from the gcc2 side.