When mosquitto is included as subdirectory, `CMAKE_SOURCE_DIR` does not refer to the mosquitto top level CMake file, but to the whole project top level CMake.
Use `PROJECT_SOURCE_DIR` instead to refer to the right CMake in both contextes.
Signed-off-by: Pierre Hallot <hallotpierre@gmail.com>
This now handles the case where we are building from the released tar, or
building from git if xsltproc is available, or building from git if xsltproc
is not available.
Pierre Hallot
Roger A. Light