Fix up linker flags for gdexample library.

Author: enetheru

cmake/common_compiler_flags.cmake

@@ -119,6 +119,13 @@ target_link_options(${PROJECT_NAME} PRIVATE
     $<$<OR:${IS_CLANG},${IS_GNU}>:
         -static-libgcc
         -static-libstdc++
+    >
+    # reading up on RPATH this is only relevant for unix based systems
+    # https://stackoverflow.com/questions/107888/is-there-a-windows-msvc-equivalent-to-the-rpath-linker-flag
+    # Is probably worth putting it behind another guard in the future.
+    # It appears that gcc silently ignores it on windows
+    # It's also probably unnecessary to be explicitly stated as CMake has a target property for it.
+    $<${IS_GNU}:
         -Wl,-R,'$$ORIGIN'
     >
 )

test/CMakeLists.txt

@@ -15,10 +15,15 @@ else()
 	message(FATAL_ERROR "Not implemented support for ${CMAKE_SYSTEM_NAME}")
 endif()
 
+set( IS_CLANG "$<OR:$<CXX_COMPILER_ID:AppleClang>,$<CXX_COMPILER_ID:Clang>>" )
+set( IS_GNU "$<CXX_COMPILER_ID:GNU>" )
+set( IS_MSVC "$<CXX_COMPILER_ID:MSVC>" )
+
+
 # Define our godot-cpp library
 add_library(${PROJECT_NAME} SHARED EXCLUDE_FROM_ALL )
 
-target_sources( ${PROJECT_NAME}
+target_sources(${PROJECT_NAME}
         PRIVATE
         src/example.cpp
         src/example.h
@@ -27,13 +32,34 @@ target_sources( ${PROJECT_NAME}
         src/tests.h
 )
 
-target_link_libraries( ${PROJECT_NAME}
+target_link_libraries(${PROJECT_NAME}
         PRIVATE
         godot::cpp )
 
+target_compile_options(${PROJECT_NAME}
+        PRIVATE
+        $<$<OR:${IS_CLANG},${IS_GNU}>:
+            -fPIC
+            -Wwrite-strings
+        >
+)
+
+target_link_options( ${PROJECT_NAME}
+        PRIVATE
+        $<$<OR:${IS_CLANG},${IS_GNU}>:
+            -static-libgcc
+            -static-libstdc++
+        >
+        $<${IS_GNU}: # see comments in the cmake/common_compiler_flags.cmake
+            -Wl,-R,'$$ORIGIN'
+        >
+)
+
 set_target_properties( ${PROJECT_NAME}
         PROPERTIES
         OUTPUT_NAME "gdexample"
+        POSITION_INDEPENDENT_CODE ON
+        BUILD_RPATH_USE_ORIGIN ON
         LIBRARY_OUTPUT_DIRECTORY ${CMAKE_SOURCE_DIR}/bin/${TARGET_PATH}
         RUNTIME_OUTPUT_DIRECTORY ${CMAKE_SOURCE_DIR}/bin/${TARGET_PATH}
 )