Resolve unintended fork. #2652

Job	Run time
build (gcc)	3m 20s
build (gcc, CFLAGS=-DTK_NO_DEPRECATED=1)	2m 25s
build (gcc, --disable-shared)	2m 38s
build (gcc, --disable-xft)	2m 53s
build (gcc, --disable-xss)	2m 2s
build (gcc, --enable-symbols)	1m 47s
build (clang)	2m 25s
build (clang, CFLAGS=-DTK_NO_DEPRECATED=1)	2m 42s
build (clang, --disable-shared)	3m 15s
build (clang, --disable-xft)	3m 17s
build (clang, --disable-xss)	2m 45s
build (clang, --enable-symbols)	1m 43s
test (gcc)	5m 34s
test (gcc, --disable-xft)	4m 14s
test (gcc, --enable-symbols)	3m 45s
	44m 45s

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