More CI woes

[Andrei Alexandrescu]

Several CI pipelines are failing for 
https://github.com/dlang/phobos/pull/7638, so I moseyed to what I 
thought would be a simple one, the doc build:

http://dtest.dlang.io/results/d42adbc33e821c4223291e64541d57ffbb5b3b0d/eb9e6443fd3231b8d086509d950283587ac6ee9e/build.log

I spent some time trying to make heads and tails of it. A few things 
that could be improved:

* It's 2942 lines long. Most of these lines are just chaff, e.g. do we 
really need to log every single cp operation, or would a "Copied all 
files" line suffice?

* The word '\Werror\W' appears in the log 25 times. Although I assume 
most are to be ignored, some occur in quite dire contexts, such as: 
"Error parsing type 'const(void function()* function() pure nothrow 
@property @nogc)': Missing ')' for 'const('". Is it possible to massage 
error messages known to be benign?

* Some of the command lines being run are printed like this:

[2020-09-20 02:25:55.606583] dautotest: Running: 'timeout' '1800' 'make' 
'-f' 'posix.mak' 'DMD=/home/dtest/DAutoTest/work/build/bin/dmd' '-j' '8' 
'MODEL=64'

Command lines are definitely something people would want to copy and 
paste from the log. They should be printed like this:

[2020-09-20 02:25:55.606583] dautotest: Running: 'timeout 1800 make -f 
posix.mak DMD=/home/dtest/DAutoTest/work/build/bin/dmd -j 8 MODEL=64'

The lines that carry actual information appear like this:

src/dmd/frontend.d(142): Error: template 
std.algorithm.iteration.each 
cannot deduce function from argument types 
!(addGlobalIdent)(const(string[])), 
candidates are:
/dev/shm/dtest/work/repo/dmd/generated/linux/release/64/../../../../../phobos/std/algorithm/iteration.d(805): 
       each(alias 
fun = "a", 
Range)(auto ref 
Range range)
   with fun = addGlobalIdent,
        Range = const(string[])
   must satisfy one of the following constraints:
       isInputRange!Range
        isStaticArray!Range
        hasMember!(Range, 
"opApply")

They have escape sequences for pretty printing with colors. Whatever 
system is producing that output should detect it's not running in a 
console and omit the escape sequences.

Thanks in advance!