safer "rm" (preceded by cd [..] &&), README about src/sage/ext/interpreters/

Author: dimpase

.gitignore

@@ -147,6 +147,7 @@ __pycache__/
 # Generated by sage_setup.autogen
 /src/sage/ext/interpreters
 !/src/sage/ext/interpreters/meson.build
+!/src/sage/ext/interpreters/README
 
 # Generated Cython files
 *.so

Makefile

@@ -122,7 +122,7 @@ sagelib-clean:
 	     rm -rf c_lib .cython_version cython_debug; \
 	     rm -rf build; find . -name '*.pyc' -o -name "*.so" | xargs rm -f; \
 	     rm -f $$(find . -name "*.pyx" | sed 's/\(.*\)[.]pyx$$/\1.c \1.cpp/'); \
-	     cd sage/ext/interpreters/; rm -f *.so *.c *.h *.py* *.pxd) \
+	     cd sage/ext/interpreters/ && rm -f *.so *.c *.h *.py* *.pxd) \
 	    && (cd "$(SAGE_ROOT)/build/pkgs/sagelib/src/" && rm -rf build); \
 	fi
 

src/sage/ext/interpreters/README

@@ -0,0 +1 @@
+The files in this directory, except meson.build, are autogenerated by sage_setup.autogen