Change all CMAKE_SOURCE_DIR to CMAKE_CURRENT_SOURCE_DIR

shared/cmake/libigl.cmake

@@ -479,7 +479,7 @@ install(TARGETS ${LIBIGL_ALL_MODULES} EXPORT igl-export
 )
 
 foreach(HEADERS ${LIBIGL_INSTALL_HEADERS})
-  file(GLOB HEADER_FILES "${CMAKE_SOURCE_DIR}/../include/${HEADERS}/*.h")
+  file(GLOB HEADER_FILES "${CMAKE_CURRENT_SOURCE_DIR}/../include/${HEADERS}/*.h")
   install(
     FILES ${HEADER_FILES}
     DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}/${HEADERS}