When using solidity as a third-party library (include it into our
project using FetchContent), we encountered a strange compilation error.
For some reason, cmake considers the root directory of the project as
the root directory of the dependency (solidity). This is because
solidity is incorrectly using CMAKE_SOURCE_DIR variable, which should be
PROJECT_SOURCE_DIR (The former one refers to the top-level source
directory that contains a CMakeLists.txt, while the latter refers to the
source directory of the most recent project() command)
I've created a repo for demonstration (https://github.com/junaire/test-solidity-fetch-content)
Signed-off-by: Jun Zhang <jun@junz.org>
