feat(Core/Build): add the possibility to link libraries dynamically (#5348)

src/cmake/compiler/clang/settings.cmake

@@ -8,6 +8,14 @@ target_compile_definitions(acore-compile-option-interface
   INTERFACE
     -D_BUILD_DIRECTIVE="${CMAKE_BUILD_TYPE}")
 
+set(CLANG_EXPECTED_VERSION 6.0.0)
+
+if(CMAKE_CXX_COMPILER_VERSION VERSION_LESS CLANG_EXPECTED_VERSION)
+  message(FATAL_ERROR "Clang: AzerothCore requires version ${CLANG_EXPECTED_VERSION} to build but found ${CMAKE_CXX_COMPILER_VERSION}")
+else()
+  message(STATUS "Clang: Minimum version required is ${CLANG_EXPECTED_VERSION}, found ${CMAKE_CXX_COMPILER_VERSION} - ok!")
+endif()
+
 # This tests for a bug in clang-7 that causes linkage to fail for 64-bit from_chars (in some configurations)
 # If the clang requirement is bumped to >= clang-8, you can remove this check, as well as
 # the associated ifdef block in src/common/Utilities/StringConvert.h
@@ -59,6 +67,20 @@ target_compile_options(acore-compile-option-interface
     -Wno-narrowing
     -Wno-deprecated-register)
 
-target_compile_definitions(acore-compile-option-interface
-  INTERFACE
-    -DDEBUG=1)
+if(BUILD_SHARED_LIBS)
+    # -fPIC is needed to allow static linking in shared libs.
+    # -fvisibility=hidden sets the default visibility to hidden to prevent exporting of all symbols.
+    target_compile_options(acore-compile-option-interface
+      INTERFACE
+        -fPIC)
+
+    target_compile_options(acore-hidden-symbols-interface
+      INTERFACE
+        -fvisibility=hidden)
+
+    # --no-undefined to throw errors when there are undefined symbols
+    # (caused through missing WARHEAD_*_API macros).
+    set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} --no-undefined")
+
+    message(STATUS "Clang: Disallow undefined symbols")
+endif()