[Clang][Docs] Add new offloading flags to the clang documentation

Summary:
Some previous patches introduced the `--offload-new-driver` flag, which
is a generic way to enable the new driver, and the `--offload-host-only`
and `--offload-device-only` flags which allow users to compile for one
side, making it easier to inspect intermediate code for offloading
compilations. This patch just documents them in the command line
reference.

Author: jhuber6

clang/docs/ClangCommandLineReference.rst

@@ -238,6 +238,22 @@ Flush denormal floating point values to zero in CUDA/HIP device mode.
 
 Specify comma-separated list of triples OpenMP offloading targets to be supported
 
+.. option:: -fopenmp-new-driver, -fno-openmp-new-driver
+
+Use the new driver for OpenMP offloading.
+
+.. option:: --offload-new-driver, --no-offload-new-driver
+
+Use the new driver for offloading compilation.
+
+.. option:: --offload-host-only
+
+Only compile for the host when offloading.
+
+.. option:: --offload-device-only
+
+Only compile for the device when offloading.
+
 .. option:: -force\_cpusubtype\_ALL
 
 .. program:: clang1
@@ -801,10 +817,6 @@ Generate Interface Stub Files, emit merged text not binary.
 
 Extract API information
 
-.. option:: -fopenmp-new-driver, fno-openmp-new-driver
-
-Use the new driver for OpenMP offloading.
-
 .. option:: -fsyntax-only
 
 .. option:: -module-file-info