Use current source / binary dir when assuring out of source builds (#1527)

Co-authored-by: Jordan Bayles <bayles.jordan@gmail.com>

Author: appgurueu

include/PreventInSourceBuilds.cmake

@@ -2,8 +2,8 @@
 # This function will prevent in-source builds
 function(AssureOutOfSourceBuilds)
   # make sure the user doesn't play dirty with symlinks
-  get_filename_component(srcdir "${CMAKE_SOURCE_DIR}" REALPATH)
-  get_filename_component(bindir "${CMAKE_BINARY_DIR}" REALPATH)
+  get_filename_component(srcdir "${CMAKE_CURRENT_SOURCE_DIR}" REALPATH)
+  get_filename_component(bindir "${CMAKE_CURRENT_BINARY_DIR}" REALPATH)
 
   # disallow in-source builds
   if("${srcdir}" STREQUAL "${bindir}")