Ninja: Fix depfile binding with spaces in path

In build statements we use a single `DEP_FILE = ...` binding that is
shared between `depfile = $DEP_FILE` and `command = ... $DEP_FILE ...`
bindings in the corresponding rule.  In cases that the command's shell
argument needs quoting, add a separate `depfile = ...` binding to the
build statement to express the depfile path without quoting.  Otherwise
`ninja` tries to open a file path that contains literal quotes.

Fixes: #26287