constraints_pkgs.txt: More verbosity in example

constraints_pkgs.txt

@@ -11,7 +11,7 @@
 # [alice@localhost sage]$ export MAKE="make -j16" SAGE_NUM_THREADS=16
 # [alice@localhost sage]$ make all-sage-local
 # [alice@localhost sage]$ export PIP_CONSTRAINT="$(pwd)/constraints_pkgs.txt"
-# [alice@localhost sage]$ ./sage -sh -c 'python3 -m build pkgs/sagemath-standard'
+# [alice@localhost sage]$ ./sage -sh -c 'python3 -m build -v -v pkgs/sagemath-standard'
 #
 # Non-example: Installing the built wheel using the same
 # constraints file will fail because sagemath-standard is one