Switch gnu/usr.bin/Makefile to SUBDIR.${MK_*} optional subdir style

gnu/usr.bin/Makefile

@@ -2,48 +2,27 @@
 
 .include <src.opts.mk>
 
-SUBDIR= ${_binutils} \
-	${_cc} \
-	diff \
+SUBDIR= diff \
 	diff3 \
-	${_dtc} \
-	${_gdb} \
-	${_gperf} \
-	grep \
-	${_groff} \
-	${_tests}
+	grep
 
 SUBDIR_DEPEND_gdb= ${_binutils}
 
 .if ${MK_CXX} != "no"
-.if ${MK_GCC} != "no"
-_gperf=		gperf
-.endif
-.if ${MK_GROFF} != "no"
-_groff=		groff
-.endif
+SUBDIR.${MK_GCC}+=	gperf
+SUBDIR.${MK_GROFF}+=	groff
 .endif
 
-.if ${MK_GPL_DTC} != "no"
-_dtc=		dtc
-.endif
-
-.if ${MK_TESTS} != "no"
-_tests=		tests
-.endif
+SUBDIR.${MK_BINUTILS}+=	binutils
+SUBDIR.${MK_DIALOG}+=	dialog
 
 .if ${MK_BINUTILS} != "no"
-_binutils=	binutils
-.if ${MK_GDB} != "no"
-_gdb=		gdb
-.endif
+SUBDIR.${MK_GDB}+=	gdb
 .endif
 
-.if ${MK_GCC} != "no"
-_cc=		cc
-.endif
-
-SUBDIR.${MK_DIALOG}+=	dialog
+SUBDIR.${MK_GCC}+=	cc
+SUBDIR.${MK_GPL_DTC}+=	dtc
+SUBDIR.${MK_TESTS}+=	tests
 
 SUBDIR_PARALLEL=