Improve the handling of /external:I (#13904)
### Description
Improve the handling of "/external:I". The
"onnxruntime_external_lib_include_dir" variable may be:
1. A simple file path
2. A cmake generator expression like "$<INSTALL_INTERFACE:include>",
"$<TARGET_PROPERTY:onnx_proto,INTERFACE_INCLUDE_DIRECTORIES>",
"$<BUILD_INTERFACE:xxxx>". It seems that we can't simply put them in to
the "target_compile_options" line. So this PR tries to parse the
expression and extract the part we need out.
### Motivation and Context
Resolve the Github issue: https://github.com/microsoft/onnxruntime/issues/13893
