- Added clearer structure by grouping the options into logical sections.
- Expanded the details for many of the options.
- Added Examples section to show how to use the various commands.
- Specifically highlighted that the contents of SOURCE_DIR may be lost
  if a download method is also provided.
- Updated argument-matching regex to be more robust and account for the
  varying leading spaces before keywords in the docs.
- Updated tests to account for slightly changed error messages.

6c80e958 cmCTest: Add missing switch case fallthrough markup
Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !1027

d8e6cd9e IAR: Improve support for IAR ARM Compiler
0b1a2876 Add a CMAKE_<LANG>_COMPILER_ARCHITECTURE_ID variable
fea7d69d Store CMAKE_ASM_COMPILER_VERSION persistently
d2a8b5ce CMakeDetermineASMCompiler: Fix small copy-paste mistake
a2112257 Add infrastructure to use language extensions without any standard
8cd28bb0 cmLocalGenerator: Switch order of <LANG>_{EXTENSIONS,STANDARD} check
0fc2d78e cmLocalGenerator: Simplify logic for language standard or extension flag
Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !991

d1713d8b VS: connect /Y- compiler option with "Not Using Precompiled Headers"
Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !1026

796b8fcb FindDoxygen: Create DOXYGEN_OUTPUT_DIRECTORY if it doesn't exist
Acked-by: Kitware Robot <kwrobot@kitware.com>
Reviewed-by: Craig Scott <craig.scott@crascit.com>
Merge-request: !1019

If the doxygen output directory does not exist, create it prior to
running the doxygen commands.

251bcbed Autogen: Continue search for FOO_p.h when FOO.h was found
Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !1022

16d49525 clang-format.bash: Fix error message when clang-format is not found
Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !1029

Do not refer to a variable we just determined is empty to get the
name of the tool for the error message.  Just hard-code the name.

Without this, GCC 7 warns.
Reported-by: Rolf Eike Beer <eike@sf-mail.de>

82a5c2c6 VS: Fix support for '/guard:cf' linker flag
Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !1018

83d8acee Autogen: Check .moc header name against SKIP list
Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !1017

The change allows to selectively disable PrecompiledHeaders.
Despite the `$(VCTargetsPath)/1033/cl.xml` contains an empty value for switch,
for effectively turn off setting need to use /Y- option as described on msdn:
https://msdn.microsoft.com/en-us/library/1hy7a92h.aspx

When encountering an #include "FOO.moc" statement where
FOO.hpp was chosen over FOO.cpp as the moc source, the
FOO.hpp name was not checked against the moc SKIP list.

Although `$(VCTargetsPath)/1033/link.xml` for v140 and v141 toolsets
contains an entry for `LinkControlFlowGuard`, it does not work when used
in a `.vcxproj` file.  Drop our link flag table entries for these
toolsets so that the flag will be passed via `AdditionalOptions`.

ab533e48 Help: Document server-mode protocol versions more clearly
Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !1015

c2a6df94 Xcode: Use correct Object Library paths for cross-SDK builds
Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !1016

97a9a356 FindDoxygen: Use a stable reference to the location of global resources
Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !1014

FindDoxygen generates some files based on the version of Doxygen whose
content will not vary across a project and are therefore a global
resource that can be shared by all calls to `find_package(Doxygen)` and
to `doxygen_add_docs`.  We currently use `${PROJECT_BINARY_DIR}` to
reference their location, but this is not stable because `project()`
calls in a subdirectory can change it.  Use `${CMAKE_BINARY_DIR}`
instead.
Reviewed-by: Craig Scott <craig.scott@crascit.com>
Fixes: #17022

Make the implementation for this compiler more complete.

IAR has multiple C++ modes, historically they were reduced c++ versions
for embedded that gradually improved to the full standard (which can be
reduced again by e.g. disabling rtti and exceptions).  The new
implementation picks the best available, but the c++ mode can also be
overridden by defining `CMAKE_IAR_CXX_FLAG`.

Add C/C++ standard flags so that all modes up to and including the last
supported standard are defined.

Fixes: #16826

Compilers such as MSVC and IAR may have variants that target different
architectures.  We have been using a `MSVC_<LANG>_ARCHITECTURE_ID`
variable to hold this information for MSVC.  Add an alternative with a
more general name (later we can port MSVC to it too).

This additional information may be needed to generate proper invocations
of the compiler based on its architecture variant.