bootstrap: Override CMAKE_OSX_SYSROOT when building compiler-rt

Similarly to what was previously done for the `llvm` step.

src/bootstrap/src/core/build_steps/llvm.rs

@@ -385,9 +385,6 @@ fn run(self, builder: &Builder<'_>) -> LlvmResult {
             || target.contains("apple-watchos")
             || target.contains("apple-visionos")
         {
-            // These two defines prevent CMake from automatically trying to add a MacOSX sysroot, which leads to a compiler error.
-            cfg.define("CMAKE_OSX_SYSROOT", "/");
-            cfg.define("CMAKE_OSX_DEPLOYMENT_TARGET", "");
             // Prevent cmake from adding -bundle to CFLAGS automatically, which leads to a compiler error because "-bitcode_bundle" also gets added.
             cfg.define("LLVM_ENABLE_PLUGINS", "OFF");
             // Zlib fails to link properly, leading to a compiler error.
@@ -703,6 +700,10 @@ fn configure_cmake(
                 //
                 // So for now we set it to "Darwin" on all Apple platforms.
                 cfg.define("CMAKE_SYSTEM_NAME", "Darwin");
+
+                // These two defines prevent CMake from automatically trying to add a MacOSX sysroot, which leads to a compiler error.
+                cfg.define("CMAKE_OSX_SYSROOT", "/");
+                cfg.define("CMAKE_OSX_DEPLOYMENT_TARGET", "");
             }
 
             // Make sure that CMake does not build universal binaries on macOS.