CMake: link gost.so statically to its caller

[yanovich]

If any executable loads gost.so, the executable already either has libcrypto.so loaded or is statically linked against libcrypto.a. Anyway it already has all libcrypto (and libssl) symbols present.

Without this patch gost.so is linked against libcrypto.so. As a result, a diamond dependency is introduced. If gost.so is then loaded by an executable which is statically linked against libcrypto, ld will insist on loading libcripto.so, despite the executable already having all necessary symbols. When the executable is statically linked, shared objects for libcrypto and libssl are usually not built, ld won't find them, and the caller will crush.

The patch removes this unnecessary link dependency in gost.so, allowing it to be used by executables which are statically linked against libcrypto.