Update INSTALL.md

Author: clessig

INSTALL.md

@@ -17,6 +17,9 @@ export PATH=~/.uv:$PATH
 %>uv sync
  
 # install flash_attn which is not uv compatible
+# (this step might take very long, it is faster when ninja is available but then
+# MAX_JOBS=4 should be set as environment variable; the step might need to be run
+# on a compute node to ensure the correct CUDA environment is available) 
 %>uv pip install torch
 %>uv pip install flash_attn --no-build-isolation