Update on "Build optimized operators lib with -fexceptions"

It should be permissible for this library to use exceptions, since it is not required to supported embedded systems.

TODO: presumably we need to manage rollout of the torchgen patch?

Differential Revision: [D67904052](https://our.internmc.facebook.com/intern/diff/D67904052/)

[ghstack-poisoned]

Author: Github Executorch

build/build_apple_frameworks.sh

@@ -188,7 +188,7 @@ echo "Exporting headers"
 mkdir -p "$HEADERS_PATH"
 
 # Set BUCK2 to the path of the buck2 executable in $OUTPUT/*/buck2-bin/buck2-*
-BUCK2=$(find . -type f -path '*/buck2-bin/buck2-*' | head -n 1)
+BUCK2=$(find $SOURCE_ROOT_DIR -type f -path '*/buck2-bin/buck2-*' | head -n 1)
 if [[ -z "$BUCK2" ]]; then
   echo "Could not find buck2 executable in any buck2-bin directory under $OUTPUT"
   BUCK2=$(which buck2)
@@ -201,6 +201,20 @@ check_command "$BUCK2"
   //extension/tensor: \
 | rsync -av --files-from=- "$SOURCE_ROOT_DIR" "$HEADERS_PATH/executorch"
 
+# HACK: XCFrameworks don't appear to support exporting any build
+# options, but we need the following:
+# - runtime/core/portable/type/c10 reachable with `#include <c10/...>`
+# - exported -DC10_USING_CUSTOM_GENERATED_MACROS compiler flag
+# So, just patch our generated framework to do that.
+sed -i '' '1i\
+#define C10_USING_CUSTOM_GENERATED_MACROS
+' $SOURCE_ROOT_DIR/runtime/core/portable_type/c10/macros/Macros.h
+sed -i '' '1i\
+#define C10_USING_CUSTOM_GENERATED_MACROS
+' $SOURCE_ROOT_DIR/runtime/core/portable_type/c10/macros/Export.h
+cp -r $SOURCE_ROOT_DIR/runtime/core/portable_type/c10 "$HEADERS_PATH/"
+
+
 cp "$SOURCE_ROOT_DIR/extension/apple/ExecuTorch/Exported/"*.h "$HEADERS_PATH/executorch"
 cp "$SOURCE_ROOT_DIR/extension/apple/ExecuTorch/Exported/"*.modulemap "$HEADERS_PATH"