Fix --gc-sections linking error on github macos-15-x86_64.

This forces `CMAKE_REQUIRED_FLAGS` to be treated as a string instead of list,
so none of the args get dropped when passed through `check_c_source_compiles`.

PiperOrigin-RevId: 886717366
Change-Id: I43104d73aa2185a6e2f359cf4195d05d547020b5

Author: copybara-github

cmake/MujocoLinkOptions.cmake

@@ -43,12 +43,12 @@ function(get_mujoco_extra_link_options OUTPUT_VAR)
         endif()
       endif()
 
-      set(CMAKE_REQUIRED_FLAGS ${EXTRA_LINK_OPTIONS} "-Wl,--gc-sections")
+      set(CMAKE_REQUIRED_FLAGS "${EXTRA_LINK_OPTIONS} -Wl,--gc-sections")
       check_c_source_compiles("int main() {}" SUPPORTS_GC_SECTIONS)
       if(SUPPORTS_GC_SECTIONS)
         set(EXTRA_LINK_OPTIONS ${EXTRA_LINK_OPTIONS} -Wl,--gc-sections)
       else()
-        set(CMAKE_REQUIRED_FLAGS ${EXTRA_LINK_OPTIONS} "-Wl,-dead_strip")
+        set(CMAKE_REQUIRED_FLAGS "${EXTRA_LINK_OPTIONS} -Wl,-dead_strip")
         check_c_source_compiles("int main() {}" SUPPORTS_DEAD_STRIP)
         if(SUPPORTS_DEAD_STRIP)
           set(EXTRA_LINK_OPTIONS ${EXTRA_LINK_OPTIONS} -Wl,-dead_strip)