Use correct CMake base directory offset

CMAKE_SOURCE_DIR is the top-level directory of a project, but if you include
this as a dependency, the file check locations won't exist at the top level
of any parent project.

CMAKE_CURRENT_SOURCE_DIR is the actual directory of the current project()
regardless of compile mode (standalone or included in another project).

CMakeLists.txt

@@ -8,17 +8,17 @@ project (LibreSSL C)
 
 enable_testing()
 
-file(READ ${CMAKE_SOURCE_DIR}/ssl/VERSION SSL_VERSION)
+file(READ ${CMAKE_CURRENT_SOURCE_DIR}/ssl/VERSION SSL_VERSION)
 string(STRIP ${SSL_VERSION} SSL_VERSION)
 string(REPLACE ":" "." SSL_VERSION ${SSL_VERSION})
 string(REGEX REPLACE "\\..*" "" SSL_MAJOR_VERSION ${SSL_VERSION})
 
-file(READ ${CMAKE_SOURCE_DIR}/crypto/VERSION CRYPTO_VERSION)
+file(READ ${CMAKE_CURRENT_SOURCE_DIR}/crypto/VERSION CRYPTO_VERSION)
 string(STRIP ${CRYPTO_VERSION} CRYPTO_VERSION)
 string(REPLACE ":" "." CRYPTO_VERSION ${CRYPTO_VERSION})
 string(REGEX REPLACE "\\..*" "" CRYPTO_MAJOR_VERSION ${CRYPTO_VERSION})
 
-file(READ ${CMAKE_SOURCE_DIR}/tls/VERSION TLS_VERSION)
+file(READ ${CMAKE_CURRENT_SOURCE_DIR}/tls/VERSION TLS_VERSION)
 string(STRIP ${TLS_VERSION} TLS_VERSION)
 string(REPLACE ":" "." TLS_VERSION ${TLS_VERSION})
 string(REGEX REPLACE "\\..*" "" TLS_MAJOR_VERSION ${TLS_VERSION})