Android: Fix condition detecting no APIs found in the NDK

Hi, while building aws-lc for android using CMake, I noticed the wrong error message where printed to me. By reading the code, it seems that using the "${}" syntax with STREQUAL has been forgotten inside the Android-Determine.cmake. By changing that I have indeed seen the right error message. I've done a small repro case on compiler explorer here to show the error.

By greping STREQUAL "" I've seen several places where this error might also occur, maybe another issue should be filled for that.

Fixes: #26210 (closed)