SConstruct: Prepend OIIO lib path to test env to support custom OIIO build.

Nuke 13.2 requires OIIO build with boost 1.70.0 so we need to prepend
the lib path to the LD_LIBRARY_PATH for this custom OIIO build to used
as runtime.

Author: lucienfostier

SConstruct

@@ -2571,6 +2571,8 @@ nukeTestEnv["ENV"]["LM_LICENSE_FILE"] = nukeTestEnv["NUKE_LICENSE_FILE"]
 nukeTestEnv["ENV"]["foundry_LICENSE"] = nukeTestEnv["NUKE_LICENSE_FILE"]
 nukeTestEnv["ENV"]["NUKE_PATH"] = "plugins/nuke"
 nukeTestEnv["ENV"]["IECORE_OP_PATHS"] = "test/IECoreNuke/ops:test/IECore/ops"
+# prepend OIIO LIB PATH to library path to support custom OIIO with specific dependencies
+nukeTestEnv["ENV"][libraryPathEnvVar] = "{}:{}".format( nukeTestEnv.subst( "$OIIO_LIB_PATH" ), nukeTestEnv["ENV"][libraryPathEnvVar] )
 
 if doConfigure :