Core: Fix a -Wshadow warning in gcc 11

This moves the only direct call to zlib’s crc32() into its own
translation unit, but that operation is cold enough that this won’t
matter in the slightest.  crc32_z() would be more appropriate, but
Android has an older zlib version…

Source/Core/Common/CMakeLists.txt

@@ -25,6 +25,8 @@ add_library(common
   Config/Layer.cpp
   Config/Layer.h
   CPUDetect.h
+  CRC32.cpp
+  CRC32.h
   Crypto/AES.cpp
   Crypto/AES.h
   Crypto/bn.cpp