buildsys: prefer the form HEADERS_RM-$(<config>)

Fix removal of sgtty.h using HEADERS_RM-$(<config>) syntax.
Sort it alphabetically.

Signed-off-by: Carmelo Amoroso <carmelo.amoroso@st.com>

Makefile.in

@@ -222,9 +222,6 @@ HEADERS_RM- := \
 	rpc/des_crypt.h \
 	rpc/key_prot.h \
 	rpc/rpc_des.h
-ifeq ($(UCLIBC_STRICT_HEADERS),y)
-HEADERS_RM- += sgtty.h
-endif
 HEADERS_RM-$(HAVE_SHARED)                    += dlfcn.h bits/dlfcn.h
 HEADERS_RM-$(PTHREADS_DEBUG_SUPPORT)         += thread_db.h
 HEADERS_RM-$(UCLIBC_HAS_BSD_ERR)             += err.h
@@ -275,6 +272,7 @@ HEADERS_RM-$(UCLIBC_LINUX_SPECIFIC)          += sys/fsuid.h sys/inotify.h sys/pe
 	sys/sysctl.h \
 	sys/sysinfo.h \
 	sys/vfs.h
+HEADERS_RM-$(UCLIBC_STRICT_HEADERS) += sgtty.h
 HEADERS_RM-$(UCLIBC_SUPPORT_AI_ADDRCONFIG)   += ifaddrs.h
 HEADERS_RM-$(UCLIBC_SV4_DEPRECATED)          += ustat.h sys/ustat.h bits/ustat.h
 HEADERS_RM-$(UCLIBC_SUSV3_LEGACY)            += sys/timeb.h regexp.h