git: <sys.mk>: Fix ${SHELL} to ignore the environment

[Aaron LI]

commit 958532e26a930505ae3ebf66d94d0c9dde9cd487
Author: Aaron LI <aly at aaronly.me>
Date:   Sun Apr 5 12:12:24 2026 +0800

    <sys.mk>: Fix ${SHELL} to ignore the environment
    
    From the POSIX standard [1]:
    > The SHELL macro shall be treated specially. It shall be provided by
    > make and set to the pathname of the shell command language interpreter
    > (see sh). The SHELL environment variable shall not affect the value of
    > the SHELL macro. If SHELL is defined in the makefile or is specified
    > on the command line, it shall replace the original value of the SHELL
    > macro, but shall not affect the SHELL environment variable. Other
    > effects of defining SHELL in the makefile or on the command line are
    > implementation-defined.
    
    So fix ${SHELL} to be ${.SHELL:Ush}, making it a Bourne/POSIX shell
    regardless of the user's interactive shell, so that it's suitable for
    use in the makefiles.  This is obtained from 'contrib/bmake/mk/sys.mk'.
    
    [1] https://pubs.opengroup.org/onlinepubs/9799919799/utilities/make.html#tag_20_76_13_05

Summary of changes:
 share/mk/sys.mk | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

http://gitweb.dragonflybsd.org/dragonfly.git/commitdiff/958532e26a930505ae3ebf66d94d0c9dde9cd487


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