Replace most call to grep in run-make by a script that cat the input.
Introduced a new `src/etc/cat-and-grep.sh` script (called in run-make as `$(CGREP)`), which prints the input and do a grep simultaneously. This is mainly used to debug spurious failures in run-make, such as the spurious error in #45810, as well as real errors such as #46126.
(cc #40713)
Some `grep` still remains, mainly the `grep -c` calls that count the number of matches and print the result to stdout.
77ab3a1d5f