Fix most cases of bsd.progs.mk running duplicate or missing commands.

This mostly fixes an interaction with bsd.test.mk with PROGS and SCRIPTS.
This was most notable with 'make clean' and 'make install', which r281055
and r272055 attempted to address but were inadequate.

It also addresses similar issues in bsd.progs.mk when not using bsd.test.mk.

This also fixes cases of NOT running commands in the parent when using
bsd.progs.mk:
  - 'make clean' was not run for the main process for Makefiles which had both
    FILES and SUBDIR but no PROGS or SCRIPTS.  This usually was just a
    leftover Kyuafile.auto.  One such example is usr.bin/bmake/tests/sysmk/t1/2.
  - 'make obj' was not running in the current directory with bsd.test.mk due
    to early inclusion of bsd.subdir.mk.  This was not really a problem due to
    the SUBDIRS using 'mkdir -p' for their objdirs.

There were subtle bugs causing this wrong behavior:
  1. bsd.progs.mk needs to set SCRIPTS to empty when recursing to avoid
     the sub-makes from installing, cleaning or building the SCRIPTS;
     only the parent make should be doing this.  r281055 effectively did
     the same but wasn't enough.
  2. CLEANFILES may contain (especially from *.test.mk) files which only
     the parent should clean, such as from FILES and SCRIPTS.  To resolve
     sub-makes also cleaning these, reset CLEANFILES and CLEANDIRS in the
     children before including bsd.prog.mk.  A tempting alternative would be
     to only handle CLEANFILES in the parent but then the child bsd.prog.mk
     CLEANFILES of per-PROGS wouldn't be setup.
  3. bsd.subdir.mk was included too soon in bsd.test.mk.  It needs to be
     included after bsd.prog.mk as the SCRIPTS logic is short-circuitted if
     'install:' is already defined (which bsd.subdir.mk does).  There is
     actually no need to include bsd.subdir.mk from bsd.test.mk as bsd.prog.mk
     and bsd.obj.mk will do so in the proper order.  The description in r257095
     covers this for FILES and was fixed differently, though changing the
     handling of target(install) in bsd.prog.mk may make sense after more
     research.
  4. bsd.progs.mk had extra logic to handle recursing SCRIPTS if PROGS was
     empty, which isn't its business to be doing.  SCRIPTS is handled fine
     by bsd.prog.mk.  This mostly reverts and reworks the fix in r259209 and
     partially reverts r272055.
  5. bsd.progs.mk has no need to depend 'all:' on SCRIPTS and FILES.  These
     are handled by bsd.prog.mk/bsd.files.mk fine.  This also partially reverts
     r272055.
  6. bsd.progs.mk was not drop-in safe for bsd.prog.mk.  Move the PROGS
     check from r273186 to allow it to be used safely.

Specific tested cases:
  SCRIPTS:no PROGS:no FILES:yes SUBDIR:yes
    usr.bin/bmake/tests/sysmk/t1/2

  SCRIPTS:yes PROGS:no FILES:yes SUBDIR:no
    usr.bin/bmake/tests/sysmk/t1/2/1

  SCRIPTS:yes PROGS:yes FILES:yes SUBDIR:yes
    lib/libthr/tests

  SCRIPTS:yes PROGS:no FILES:yes SUBDIR:no
    usr.bin/yacc/tests
    libexec/atf/atf-sh/tests

A full buildworld/installworld/clean comparison with mtree was also done.
The only relevant difference was the new fixed behavior of removing
Kyuafile.auto from the objdir in 'clean'.

Converting SCRIPTS to be a special case FILES group will make this less
fragile and is being explored.

One known remaining issue is 'cleandepend' removing the tags files for
every recursive call.

Note that the 'make clean' command runs for the CURDIR last, which can make
it appear to run multiple times when cleaning in tests/, but each command is
for a SUBDIR returning up the chain.  This is purely bsd.subdir.mk behavior.

PR:		191055
PR:		191955
MFC after:	2 weeks
Sponsored by:	EMC / Isilon Storage Division

share/mk/bsd.prog.mk

@@ -258,7 +258,7 @@ realinstall: _maninstall
 .ORDER: beforeinstall _maninstall
 .endif
 
-.endif
+.endif	# !target(install)
 
 .if !target(lint)
 lint: ${SRCS:M*.c}

share/mk/bsd.progs.mk

@@ -60,25 +60,27 @@ UPDATE_DEPENDFILE ?= NO
 
 # prog.mk will do the rest
 .else
-all: ${FILES} ${PROGS} ${SCRIPTS}
+all: ${PROGS}
 
 # We cannot capture dependencies for meta mode here
 UPDATE_DEPENDFILE = NO
 # nor can we safely run in parallel.
 .NOTPARALLEL:
 .endif
-.endif
+.endif	# PROGS || PROGS_CXX
 
-# The non-recursive call to bsd.progs.mk will handle FILES; NUL out
-# FILESGROUPS so recursive calls don't duplicate the work
+# These are handled by the main make process.
 .ifdef _RECURSING_PROGS
-FILESGROUPS=
+_PROGS_GLOBAL_VARS= CLEANFILES CLEANDIRS FILESGROUPS SCRIPTS
+.for v in ${_PROGS_GLOBAL_VARS}
+$v =
+.endfor
 .endif
 
 # handle being called [bsd.]progs.mk
 .include <bsd.prog.mk>
 
-.ifndef _RECURSING_PROGS
+.if !empty(PROGS) && !defined(_RECURSING_PROGS)
 # tell progs.mk we might want to install things
 PROGS_TARGETS+= checkdpadd clean cleandepend cleandir cleanobj depend install
 
@@ -88,12 +90,14 @@ PROGS_TARGETS+= checkdpadd clean cleandepend cleandir cleanobj depend install
 x.$p= PROG_CXX=$p
 .endif
 
+# Main PROG target
 $p ${p}_p: .PHONY .MAKE
 	(cd ${.CURDIR} && \
 	    DEPENDFILE=.depend.$p \
 	    ${MAKE} -f ${MAKEFILE} _RECURSING_PROGS= \
 	    SUBDIR= PROG=$p ${x.$p})
 
+# Pseudo targets for PROG, such as 'install'.
 .for t in ${PROGS_TARGETS:O:u}
 $p.$t: .PHONY .MAKE
 	(cd ${.CURDIR} && \
@@ -103,21 +107,8 @@ $p.$t: .PHONY .MAKE
 .endfor
 .endfor
 
-.if !empty(PROGS)
+# Depend main pseudo targets on all PROG.pseudo targets too.
 .for t in ${PROGS_TARGETS:O:u}
 $t: ${PROGS:%=%.$t}
 .endfor
 .endif
-
-.if empty(PROGS) && !empty(SCRIPTS)
-
-.for t in ${PROGS_TARGETS:O:u}
-scripts.$t: .PHONY .MAKE
-	(cd ${.CURDIR} && ${MAKE} -f ${MAKEFILE} SUBDIR= _RECURSING_PROGS= \
-	    $t)
-$t: scripts.$t
-.endfor
-
-.endif
-
-.endif

share/mk/bsd.test.mk

@@ -91,10 +91,6 @@ test: beforetest realtest
 test: aftertest
 .endif
 
-.if !empty(SUBDIR)
-.include <bsd.subdir.mk>
-.endif
-
 .ifdef PROG
 # we came here via bsd.progs.mk below
 # parent will do staging.