Refactor LibToOSO tool (#2691)

* Localize the compileOSL() code, this removes the dependency on MaterialXRender
* Add optional dependency on liboslcomp, which allows compiling of the osos without using std::system. This significantly speeds up compilation time, on my machine dropping from about a minute for the entire data library to about 15 seconds.
* With liboslcomp, we can avoid writing the OSL source to disk - saving space. This is controlled by a command line argument
* Add command line arguments to specify data library location
* Add argument to avoid writing the MaterialX document for the implementation elements, this may be helpful for those not using MaterialX shader generation.

Author: ld-kerley

source/MaterialXGenOsl/CMakeLists.txt

@@ -14,22 +14,26 @@ mx_add_library(MaterialXGenOsl
     EXPORT_DEFINE
         MATERIALX_GENOSL_EXPORTS)
 
-# FIXME: LibsToOso has a dependency on the OslRenderer.
-if (MATERIALX_BUILD_OSOS AND MATERIALX_BUILD_RENDER)
+if (MATERIALX_BUILD_OSOS)
     file(GLOB GenNodes_SRC "${CMAKE_CURRENT_SOURCE_DIR}/LibsToOso.cpp")
 
-    set(MATERIALX_LIBRARIES
-        MaterialXCore
-        MaterialXFormat
-        MaterialXGenShader
-        MaterialXGenOsl
-        MaterialXRenderOsl)
-
     add_executable(MaterialXGenOsl_LibsToOso ${GenNodes_SRC})
 
-    target_link_libraries(
-        MaterialXGenOsl_LibsToOso
-        ${MATERIALX_LIBRARIES})
+    target_link_libraries(MaterialXGenOsl_LibsToOso
+        PRIVATE
+            MaterialXCore
+            MaterialXFormat
+            MaterialXGenShader
+            MaterialXGenOsl)
+
+    if (OSL_FOUND)
+        target_link_libraries(MaterialXGenOsl_LibsToOso
+            PRIVATE
+                OSL::oslcomp)
+        target_compile_definitions(MaterialXGenOsl_LibsToOso
+            PRIVATE
+                USE_OSLCOMP)
+    endif()
 
     set_target_properties(
         MaterialXGenOsl_LibsToOso PROPERTIES