Makefile: Use POSIX-compliant method to delete multiple files (for-loop)

[i3/i3] / man / Makefile

all:
        a2x -f manpage --asciidoc-opts="-f asciidoc.conf" i3.man
        a2x -f manpage --asciidoc-opts="-f asciidoc.conf" i3-msg.man
        a2x -f manpage --asciidoc-opts="-f asciidoc.conf" i3-input.man
clean:
        for file in "i3 i3-msg i3-input"; \
        do \
                rm -f $${file}.1 $${file}.html $${file}.xml; \
        done