build: Move -s additional compiler flags into linker flags, and enable it only when gcc/clang are used. (#1087)

Compiler when compiling doesn't use them in those cases and emit a
warning, which is turned into an error by `-Werror`. Unfortunately,
CPack doesn't expose the logic it uses for stripping binaries.

cmake/build_helpers.cmake

@@ -1,12 +1,12 @@
 include(FetchContent)
 
 if(IMHEX_STRIP_RELEASE)
-    set(CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE} -s")
-    set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -s")
-
     if(CMAKE_BUILD_TYPE STREQUAL "Release")
         set(CPACK_STRIP_FILES TRUE)
     endif()
+    if(CMAKE_CXX_COMPILER_ID MATCHES "GNU|Clang")
+        add_link_options($<$<CONFIG:RELEASE>:-s>)
+    endif()
 endif()
 
 macro(addDefines)