MAKEOBJDIRPREFIX fails if it has dot '.' in dir name (maybe also with some other chars)

[Enji Cooper]

> On Aug 12, 2019, at 7:38 AM, Glen Barber <gjb at FreeBSD.org> wrote:
> 
> On Mon, Aug 12, 2019 at 03:17:35PM +0200, Domagoj Smolčić wrote:
>> 11.3-RELEASE-p2
>> 
>> 
>> # make MAKEOBJDIRPREFIX=/usr/obj/usr.LOCAL buildworld
> 
> You set MAKEOBJDIRPREFIX two different ways.  Here you did not set it
> in the environment, but as a variable to make(1).  The way you did this
> below is correct.

…

>> # env MAKEOBJDIRPREFIX=/usr/obj/usr_LOCAL make buildworld
> 
> This worked for me using '.' in the path.
> 
> # env MAKEOBJDIRPREFIX=/usr/obj/usr.LOCAL make buildworld
> make[1]: "/usr/src/Makefile.inc1" line 163: SYSTEM_COMPILER: Determined that CC=cc matches the source tree.  Not bootstrapping a cross-compiler.

Hmmm… I wonder why this error case in /Makefile wasn’t tripped...

193 MAKEOBJDIRPREFIX?=      /usr/obj
194 _MAKEOBJDIRPREFIX!= /usr/bin/env -i PATH=${PATH} ${MAKE} MK_AUTO_OBJ=no \
195     ${.MAKEFLAGS:MMAKEOBJDIRPREFIX=*} __MAKE_CONF=${__MAKE_CONF} \
196     SRCCONF=${SRCCONF} SRC_ENV_CONF= \
197     -f /dev/null -V MAKEOBJDIRPREFIX dummy
198 .if !empty(_MAKEOBJDIRPREFIX)
199 .error MAKEOBJDIRPREFIX can only be set in environment or src-env.conf(5),\
200     not as a global (in make.conf(5) or src.conf(5)) or command-line variable.
201 .endif

-Enji