Add location of GitSHA2.h to include_directories

If ${CMAKE_CURRENT_SOURCE_DIR} is not the same as ${CMAKE_CURRENT_BINARY_DIR}, the build will fail because it cannot find GitSHA2.h.

This patch adds ${CMAKE_CURRENT_SOURCE_DIR} with "include_directories"

fc already does this with GitSHA3.h

(from CMakeLists.txt)
configure_file("${CMAKE_CURRENT_SOURCE_DIR}/GitSHA2.cpp.in" "${CMAKE_CURRENT_BINARY_DIR}/GitSHA2.cpp" @ONLY)
list(APPEND sources "${CMAKE_CURRENT_BINARY_DIR}/GitSHA2.cpp" GitSHA2.h)