Revert "ftw.h installation: fix inverted logic"

The logic was fine previously.
Thanks to Peter Kjellerstedt for pointing out my confusion.

This reverts commit d75f980f379dfbbe70ae8fb0956693a95af2fca2.

Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>

Makefile.in

@@ -262,7 +262,7 @@ HEADERS_RM-$(UCLIBC_HAS_BSD_ERR)             += err.h
 HEADERS_RM-$(UCLIBC_HAS_CRYPT)               += crypt.h
 HEADERS_RM-$(UCLIBC_HAS_EPOLL)               += sys/epoll.h
 HEADERS_RM-$(UCLIBC_HAS_FENV)                += fenv.h bits/fenv.h bits/fenvinline.h
-HEADERS_RM-$(if $(findstring y,$(UCLIBC_HAS_FTW)$(UCLIBC_HAS_NFTW)),,y) += ftw.h
+HEADERS_RM-$(findstring y,$(UCLIBC_HAS_FTW)$(UCLIBC_HAS_NFTW))  += ftw.h
 HEADERS_RM-$(UCLIBC_HAS_GETTEXT_AWARENESS)   += libintl.h
 HEADERS_RM-$(UCLIBC_HAS_GLIBC_CUSTOM_PRINTF) += printf.h
 HEADERS_RM-$(UCLIBC_HAS_GLOB)                += glob.h