Fix issue with llvm-rc when ZYCORE_BUILD_SHARED_LIB is enabled

[netadr]

If llvm-rc is used as the resource compiler, the following error occurs if ZYCORE_BUILD_SHARED_LIB is enabled:

llvm-rc: Error in VERSIONINFO statement (ID 1):
Non-ASCII 8-bit codepoint (�) can't be interpreted in the current codepage

This is a common issue encountered with llvm-rc, see curl/curl#7765.
Following the workaround from libcurl, this pull request changes the copyright symbol © to (C).

[flobernd]

Thanks for the workaround!