[gn build] try to fix libxml2 include path on mac after 0ec448194e29

GitOrigin-RevId: 9fa11201618d8ad3a978815d90d3e64d8e0fa310
diff --git a/utils/gn/build/BUILD.gn b/utils/gn/build/BUILD.gn
index 6f63592..907520b 100644
--- a/utils/gn/build/BUILD.gn
+++ b/utils/gn/build/BUILD.gn
@@ -283,11 +283,11 @@
     }
     cflags += [
       "-isysroot",
-      sdk_path,
+      rebase_path(sdk_path, root_build_dir),
     ]
     ldflags += [
       "-isysroot",
-      sdk_path,
+      rebase_path(sdk_path, root_build_dir),
     ]
   }
   if (sysroot != "" && current_os != "win" && is_clang) {
diff --git a/utils/gn/build/mac_sdk.gni b/utils/gn/build/mac_sdk.gni
index 51cc56c..af7044b 100644
--- a/utils/gn/build/mac_sdk.gni
+++ b/utils/gn/build/mac_sdk.gni
@@ -25,8 +25,7 @@
     iossim_sdk_path = "/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator.sdk"
   }
 } else {
-  ios_sdk_path = rebase_path(sysroot, root_build_dir) + "/iPhoneOS.sdk"
-  iossim_sdk_path =
-      rebase_path(sysroot, root_build_dir) + "/iPhoneSimulator.sdk"
-  mac_sdk_path = rebase_path(sysroot, root_build_dir) + "/MacOSX.sdk"
+  ios_sdk_path = sysroot + "/iPhoneOS.sdk"
+  iossim_sdk_path = sysroot + "/iPhoneSimulator.sdk"
+  mac_sdk_path = sysroot + "/MacOSX.sdk"
 }