CMakeLists.txt: Add possibility to build library as shared

This adds the option to build the soem library also as shared object.
Note that the default is untouched, so by default, it will still build
a static library.

The [BUILD_SHARED_LIBS](https://cmake.org/cmake/help/latest/variable/BUILD_SHARED_LIBS.html)
is the standard way of doing it, many tools use this semantics to influence
the output to be the desired type (whichever you want).

Signed-off-by: Matthias Schoepfer <[email protected]>

CMakeLists.txt

@@ -10,6 +10,8 @@ if (CMAKE_INSTALL_PREFIX_INITIALIZED_TO_DEFAULT)
   set(CMAKE_INSTALL_PREFIX ${CMAKE_CURRENT_LIST_DIR}/install)
 endif()
 
+option(BUILD_SHARED_LIBS "Build using shared libraries" OFF)
+
 set(SOEM_INCLUDE_INSTALL_DIR include/soem)
 set(SOEM_LIB_INSTALL_DIR lib)
 
@@ -69,11 +71,17 @@ file(GLOB SOEM_HEADERS soem/*.h)
 file(GLOB OSAL_HEADERS osal/osal.h osal/${OS}/*.h)
 file(GLOB OSHW_HEADERS oshw/${OS}/*.h)
 
-add_library(soem STATIC
+add_library(soem
   ${SOEM_SOURCES}
   ${OSAL_SOURCES}
   ${OSHW_SOURCES}
   ${OSHW_EXTRA_SOURCES})
+
+if (BUILD_SHARED_LIBS)
+  set_target_properties(soem PROPERTIES VERSION ${PROJECT_VERSION})
+  set_target_properties(soem PROPERTIES SOVERSION ${PROJECT_VERSION})
+endif(BUILD_SHARED_LIBS)
+
 target_link_libraries(soem ${OS_LIBS})
 
 target_include_directories(soem PUBLIC