Log Message:
mk/tools: correctly quote arguments in the tool wrapper log

Before, the tool arguments were written to the log as plain strings. Now
the arguments are properly quoted, which makes it possible to replay the
commands by copying them from the .work.log file.

This only affects tools that are shell builtins (echo, true, false), get
additional arguments (mkdir -p) or define a custom TOOLS_SCRIPT
(pkg-config, to set an environment variable; or autotools). Tools that
are symlinked to the real tool are not affected.

The calls to the compiler are already properly logged since cwrappers
takes care of that. This commit therefore makes the log entries for the
compilers and the other tools more similar.