Merge bmake-20220208

• unit-tests/Makefile: disable opt-debug-x-trace on Linux if there is any chance we have dash as .SHELL
• meta.c: use a variable to hold command line to be filtered to avoid any side effects from content of command line.

Merge commit '535c59a6a9214436f5d6643775d29808e4b3408d'

(cherry picked from commit a6f0e10b24b6011dd5f71c99848ddeef264d9ac9)