Quirk with rules producing multiple output files

[Roger Pepitone]

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TEST_TEXTS := test1.txt test2.txt test3.txt

$(TEST_TEXTS) : xtest.txt
        echo "Rebuilding $@"
        touch $(TEST_TEXTS)

xtest: $(TEST_TEXTS)

clean-xtest:
        rm $(TEST_TEXTS)

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make clean-xtest
make xtest
touch xtest.txt
make xtest


The first call to "make xtest" runs the rule 3 times, even though it
should only need to do it once.
The second call correctly only runs it once.