CMake: fix for SuperLU

It wasn't possible to use a custom superlu path.

- Added "superlu" onto the end of SUPERLU_INCLUDE_DIR
- Wasn't using SUPERLU_INCLUDE_DIR, instead used hard-coded path.
  Now use SUPERLU_INCLUDE_DIR on Linux,
  leave windows and macOS as-is with notice.

toonz/sources/CMakeLists.txt

@@ -288,7 +288,6 @@ elseif(UNIX)
     find_package(GLEW)
 
     find_package(SuperLU REQUIRED)
-    set(SUPERLU_INCLUDE_DIR ${SUPERLU_INCLUDE_DIR}/superlu)
     set(SUPERLU_LIB ${SUPERLU_LIBRARY})
 
     find_package(JPEG REQUIRED)

toonz/sources/tnzext/CMakeLists.txt

@@ -94,10 +94,19 @@ if(APPLE)
     find_library(ACCE_LIB Accelerate)
 endif()
 
-include_directories(
+if(WIN32 OR APPLE)
+    # Warning, this looks wrong,
+    # should _only_ use SUPERLU_INCLUDE_DIR, for now do this with Linux.
+    include_directories(
         SYSTEM
         ${SDKROOT}/superlu/SuperLU_4.1/SRC
-)
+    )
+else()
+    include_directories(
+        SYSTEM
+        ${SUPERLU_INCLUDE_DIR}
+    )
+endif()
 
 if(WIN32)
     target_link_libraries(tnzext