How to link iPad Air app (arm64) against existing

I have compiled armv7 static libraries (lib*.a) and i'm going to compile iPad Air app (arm64). I'm getting linker warning and then linker error:

$ lipo -info /Users/user/Documents/dev/src/iOS_Projects/iProject/libMyLib.a
input file /Users/user/Documents/dev/src/iOS_Projects/iProject/libMyLib.a is not a fat file
Non-fat file: /Users/user/Documents/dev/src/iOS_Projects/iProject/libMyLib.a is architecture: armv7

Ld: warning: ignoring file /Users/user/Documents/dev/src/iOS_Projects/iProject/libMyLib.a, file was built for archive which is not the architecture being linked (arm64): /Users/user/Documents/dev/src/iOS_Projects/iProject/libMyLib.a ignoring file

It's undesirable (and can be impossible) to recompile static libs for arm64. How can i use them?

With difficulty.

You can only switch between AArch32 state and AArch64 state at an exception boundary, so whilst e.g. 64-bit kernel/32-bit userspace is possible, it's impossible to use both in a single process. Since it's an entirely different instruction set/register layout/exception model/etc. there's no 32/64-bit interworking in the style of ARM/Thumb (which are essentially just different encodings of the same instructions).

In general (I'm not familiar with iOS specifics, but I assume it supports "legacy" AArch32 processes as Linux does):

If the libraries are completely integral to your code, your best bet is to simply give in and compile your app as 32-bit.
If you have super-crucial-absolutely-must-be-64-bit code but the library calls are not in the fast path, you could compile them into a 32-bit helper program that you spawn as an additional process and call via some form of IPC.
Otherwise you're looking at the ridiculously impractical prospect of some form of binary translation.

I gather that iOS offers no support for IPC, which rather rules out the second option in this particular case.