Swtich to gcovr For Coverage

[LeStarch]

Coverage is inherently broken due to limitations of the gcov executable. It can only be run on one directory of .o/.gcno objects at a time, and modules (e.g. Os) are permitted to span multiple directories. See: #1248

As stated in that issue there are two fixes:

1. Detect all possible output directories, run gcov on each, and merge the outputs
2. Switch to another tool which will do that same work for us

The recommendation here is to switch to gcovr and use that to perform this work.

1. gcovr runs gcov summarizes results and can even produce better formatted output (HTML)
2. gcovr fixes the issue without need to massively change our build system
3. Reduced complexity compared to doing the work ourselves.

Ramifications of this means we would be switching format for the coverage output:

------------------------------------------------------------------------------
File                                       Lines    Exec  Cover   Missing
------------------------------------------------------------------------------
File.hpp                                       1       1   100%   
FileCommon.cpp                                34       0     0%   17,20-22,24-25,27,29,31,33-36,39-42,44,46-47,49-52,54-56,58-59,63-65,68-69
IPCQueueCommon.cpp                            14       0     0%   6,8-9,11,15,17-19,21,23-25,27,30
IntervalTimerCommon.cpp                       10       0     0%   19-21,24,26-27,30-31,34-35
Linux/Directory.cpp                           59       0     0%   17,20-21,24,26,28,30-32,34-35,37-38,40-41,43-44,46,49-50,53,56-57,60-61,64,66,69,72,76,78,81-82,85-86,89,91-92,94-97,101,103,105-106,109,113,116-117,120-123,125,128-129,132-133
Linux/File.cpp                               219      80    36%   55-56,59,65,74-75,77-78,93-94,99-100,105-106,115-116,119,121-122,125,146,149,152-153,156-157,159,163-168,172,181-182,187-188,210,212-213,215-216,218-220,229-231,233,236,241,257-258,263-264,280,282-283,285-286,290-291,293-294,317,321-323,327-329,331-333,339,341-342,344-345,347-353,376,379-380,383,385-386,389,391-392,394-395,397-398,402,413-414,417-418,421,425-427,430-431,434-437,442,444-446,448,450-451,453-454,457-459,462,464-466,469-471,475-477,480-481
Linux/FileSystem.cpp                         281     116    41%   31,36-37,39-40,44-45,47-48,51-52,54-55,57-58,70,75-76,79-80,85-86,88-89,91-92,94-95,116,118-119,121-122,124-125,127-128,130,158,160,162,167,172,185,189-190,192-193,197-198,200-201,203-204,206-207,219,224-225,228-229,234-235,238-239,242-243,245-246,248-249,251-252,259-260,262,264-265,267-268,270-271,273,275,295,297-298,302-303,305-306,308-309,311,347,357,383,388,393,404,407,409-410,412-414,418-420,423-425,429-432,436-438,441,443-444,446-447,468,471-472,474-475,479-480,482-483,485-486,493-494,497-499,501-502,506-507,509-510,512-513,515,518-520,533,535-536,538-539,541-542,544-545,547,563,569,574
Linux/InterruptLock.cpp                        7       0     0%   4,7-8,10-11,14-15
Linux/WatchdogTimer.cpp                       11       0     0%   5-6,10,13-14,17-18,21-22,25-26
Log.hpp                                        1       0     0%   13
LogDefault.cpp                                 1       0     0%   9
LogPrintf.cpp                                  5       0     0%   11,15,19,32-33
MacOs/IPCQueueStub.cpp                       162       0     0%   31,33-38,40-43,45-46,54,57-58,61-63,67-69,71-72,74,77-78,82,85,87-89,91,94,96-98,100,105-106,110,112,115-116,120,124-125,129,132,134-137,143-144,148-150,154,160,164-165,168-169,173,177,179-180,182-183,186-187,190-191,194-195,198,201,203-205,208-210,215-216,220,222,224-225,229-230,233-234,236,238,240,244,249-250,254,257,259-262,265-267,272-273,277-279,283,285,287-288,292-293,296-297,299,305,310-311,315,318,320-321,324,326-327,332-333,336-337,340,343-346,348-349,352-355,357-358,361-364,366-367,370-373,375-376
MacOs/SystemResources.cpp                     48      43    89%   109-110,128-130
MemCommon.cpp                                  4       0     0%   7-8,11-12
Posix/IntervalTimer.cpp                       12       0     0%   15,18-20,25-31,33
Posix/Mutex.cpp                               21       0     0%   8-10,14,22-23,26-27,29-30,32,35-38,41-43,46-48
Posix/Task.cpp                               171      79    46%   34-35,39-40,43-44,47-48,52-53,57-58,65-68,76-79,82-86,90-95,115,130-131,137,144,150,162-164,166-168,170-172,174-176,180-184,207-212,216,225,230,234-235,238-239,241-242,244-247,249-253,255,269,277-278,281-282,285-287,290-292,298,303
Posix/TaskId.cpp                               9       0     0%   16,18,20,23,25,27,29,31,33
Pthreads/BufferQueueCommon.cpp                78      77    98%   61
Pthreads/MaxHeap/MaxHeap.cpp                 125     105    84%   56,262-263,266-269,271-273,275-278,280-284,287
Pthreads/PriorityBufferQueue.cpp              90      78    86%   73,76-77,81-82,86-88,95-98
Pthreads/Queue.cpp                           179     158    88%   63-64,70,73,79,184,188,192,237,245,297-298,300,306,322,328,334,347,356,365,374
QueueCommon.cpp                               25      18    72%   34,50,52,57-58,61-62
QueueString.cpp                               29       8    27%   10-11,14-15,22-24,27-28,31-33,36-37,40-42,48-49,52-53
TaskCommon.cpp                                19       0     0%   13-14,18-19,22-23,26-27,30-31,34-35,38-40,43,47-48,51
TaskString.cpp                                29      15    51%   10-11,14-15,22-24,27-28,31-33,36-37
ValidateFileCommon.cpp                       117      90    76%   24,39,71,79,82,106,109,128,132,134,136,138,140,142,144,148,152,154,156,158,160,162,164,166,169,185,192
ValidatedFile.cpp                             25       0     0%   19-22,24,28,30-34,36,40,42-46,48,52,54,58,60,64,66
------------------------------------------------------------------------------
TOTAL                                       1786     868    48%
------------------------------------------------------------------------------

Source-annotated "missing lines" would require extended output (e.g. HTML).

[LeStarch]

@kevin-f-ortega thoughts here?

[kevin-f-ortega]

Using gcovr sounds like a good solution. I like that it won't complicate the existing cmake, it'll fix the issue I am having, and it provides this new slick html output files.
The summary table is good, although I do have a preference for the text files gcov would output; however, this works fine.

[LeStarch]

Action: does this render ok in links browser.

[latk]

Gcovr's HTML output targets evergreen browsers with HTML5 support (Firefox/Chrome), but in practice the output is somewhat reasonable in textmode browsers like Links or Lynx as well. The main limitation will be that <details> is not supported by those, so that branch-details are always shown and leads to weird table layout. Here is how Links 2.21 renders a page from the gcovr test suite:

Note also that indentation is not preserved in browsers that don't interpret CSS styles, though that would be an easy fix if this feature were really needed.