Support older CMake

add_compile_definitions() is CMake 3.12+ only.

Author: ferdnyc

src/bindings/ruby/CMakeLists.txt

@@ -73,7 +73,7 @@ set_property(SOURCE openshot.i PROPERTY CPLUSPLUS ON)
 set_property(SOURCE openshot.i PROPERTY SWIG_MODULE_NAME openshot)
 
 ### Unbreak std::isfinite()
-add_compile_definitions(HAVE_ISFINITE=1)
+add_definitions(-DHAVE_ISFINITE=1)
 
 ### Suppress a ton of warnings in the generated SWIG C++ code
 set(SWIG_CXX_FLAGS "-Wno-unused-variable -Wno-unused-function \