options: Build maya IECoreUSD against the maya-usd plugin libraries if installed

Note:
- Autodesk does ship the USD libraries but not the header files. We
  try to find a local USD install of the version maya-usd is using and
  set the include directory respectively. If there is no compatible
  USD version present, we fall back to the cortex defined USD version
  and build `IECoreUSD` for Maya against this one.
- In the transition from python 2 to 3, maya-usd is shipped with the
  libraries for both versions, so we have to add the python major
  version suffix for Maya 2022.
  The library folders for Maya 2020.4 don't have this suffix and because
  Maya 2023 is supposed to be python3 exclusively (Autodesk release
  notes),we assume the suffix to be removed in that version again

Author: yannci

config/ie/options

@@ -326,6 +326,29 @@ if targetApp=="maya" :
 	INSTALL_COREMAYA_POST_COMMAND="scons -i -f config/ie/postCoreMayaInstall MAYA_VERSION='" + mayaVersion + "' INSTALLPREFIX="+appPrefix+" install"
 	WITH_MAYA_PLUGIN_LOADER = 1
 
+	mayaUsdVersion = mayaReg.get( "mayaUsdVersion" )
+	mayaUsdReg = IEEnv.registry["apps"]["mayaUsd"].get( mayaUsdVersion, {} ).get( platform )
+	# If the Maya usd plugin is not in the registry we build against our standalone USD version
+	if mayaUsdReg :
+		pluginUsdVersion = mayaUsdReg["usdVersion"]
+		# Maya ships the USD libraries with the installation, but not the header files... we use the one that are installed by standalone usd
+		usdReg = IEEnv.registry["apps"]["usd"].get( pluginUsdVersion, {} ).get( platform )
+		if usdReg :
+			USD_INCLUDE_PATH = os.path.join( usdReg["location"], targetApp, compatibilityVersion, "include" )
+
+			mayaLooseVersion = distutils.version.LooseVersion(mayaVersion)
+			if mayaLooseVersion >= "2022" and mayaLooseVersion < "2023":
+				# Maya 2022 installs the USD libs and the maya plugin itself for python 2 and 3. This is not the case for the 2020 version
+				# We make the assumption, that the python version suffix is for Maya 2022 only, because Maya 2023 will be python 3 exclusively.
+				mayaPythonMajorVersion = mayaReg["pythonVersion"].split(".")[0]
+				USD_LIB_PATH = os.path.join( mayaUsdReg["location"], "mayausd/USD{}/lib".format( mayaPythonMajorVersion ) )
+			else:
+				USD_LIB_PATH = os.path.join( mayaUsdReg["location"], "mayausd/USD/lib" )
+
+			# Pixar introduced a library prefix `usd_` in USD v21.11, which Autodesk does not use yet, so we have to reset the prefix.
+			# See https://github.com/Autodesk/maya-usd/issues/2108 for reference
+			USD_LIB_PREFIX = "" if mayaUsdReg.get( "usdLibPrefix" ) == "" else mayaUsdReg.get( "usdLibPrefix" ) or USD_LIB_PREFIX
+
 # find nuke if we're building for nuke
 if targetApp=="nuke" :