Override BUILD_SHARED_LIBS with SPDLOG_BUILD_SHARED

SPDLOG_BUILD_SHARED option should override BUILD_SHARED_LIBS value
in case user wants to force building spdlog as static library.

Signed-off-by: rafalmaziejuk <rafalmaziejuk@gmail.com>

CMakeLists.txt

@@ -154,7 +154,11 @@ if(NOT SPDLOG_USE_STD_FORMAT AND NOT SPDLOG_FMT_EXTERNAL AND NOT SPDLOG_FMT_EXTE
     list(APPEND SPDLOG_SRCS src/bundled_fmtlib_format.cpp)
 endif()
 
-if(SPDLOG_BUILD_SHARED OR BUILD_SHARED_LIBS)
+if(SPDLOG_BUILD_SHARED)
+    set(BUILD_SHARED_LIBS ${SPDLOG_BUILD_SHARED})
+endif()
+
+if(BUILD_SHARED_LIBS)
     if(WIN32)
         configure_file(${CMAKE_CURRENT_SOURCE_DIR}/cmake/version.rc.in ${CMAKE_CURRENT_BINARY_DIR}/version.rc @ONLY)
         list(APPEND SPDLOG_SRCS ${CMAKE_CURRENT_BINARY_DIR}/version.rc)