Fix Linux so/static build issue.

Hardened linker do not like mixing shared and static libraries
(who where compiled without -fPIC), thus simply build against the
header only version if not shared library is available.

.gitignore

@@ -81,3 +81,4 @@ cmake-build-*/
 *.tcl
 *.user
 *.sln
+/output

example/CMakeLists.txt

@@ -11,17 +11,22 @@ endif()
 # ---------------------------------------------------------------------------------------
 # Example of using shared libraries
 # ---------------------------------------------------------------------------------------
+if(SPDLOG_BUILD_SHARED OR BUILD_SHARED_LIBS)
     add_library(mylibrary SHARED mylibrary.cpp mylibrary.h)
     target_link_libraries(mylibrary PRIVATE spdlog::spdlog)
+    target_compile_definitions(mylibrary PUBLIC SPDLOG_SHARED_LIB)
     target_compile_definitions(mylibrary PUBLIC SPDLOG_COMPILED_LIB)
     
     add_executable(library_example library_example.cpp)
     target_link_libraries(library_example PRIVATE spdlog::spdlog mylibrary)
+    target_compile_definitions(library_example PUBLIC SPDLOG_SHARED_LIB)
     target_compile_definitions(library_example PUBLIC SPDLOG_COMPILED_LIB)
+else()    
+    add_library(mylibrary SHARED mylibrary.cpp mylibrary.h)
+    target_link_libraries(mylibrary PRIVATE spdlog::spdlog_header_only)
 
-if(SPDLOG_BUILD_SHARED OR BUILD_SHARED_LIBS)
-    target_compile_definitions(mylibrary PUBLIC SPDLOG_SHARED_LIB)
-    target_compile_definitions(library_example PUBLIC SPDLOG_SHARED_LIB)
+    add_executable(library_example library_example.cpp)
+    target_link_libraries(library_example PRIVATE spdlog::spdlog_header_only mylibrary)
 endif()
 
 # ---------------------------------------------------------------------------------------