For certain compilers we embed the compiler version used to build nginx
in the binary, retrievable via 'nginx -V', e.g.

  $ ./objs/nginx -V
  ...
  built by gcc 15.2.1 20250808 (Red Hat 15.2.1-1) (GCC)
  ...

However if the CFLAGS environment variable is set this would be omitted.

This is due to the compiler specific auto/cc files not being run when
the CFLAGS environment variable is set, this is so entities can set
their own compiler flags, and thus the NGX_COMPILER variable isn't set.

Nonetheless it is a useful thing to have so re-work the auto scripts to
move the version gathering out of the individual auto/cc/$NGX_CC_NAME
files and merge them into auto/cc/name.

Link: <https://github.com/nginx/nginx/issues/878>

As per POSIX, basic regular expressions have no alternations, and the
interpretation of the "\|" construct is undefined.  At least on MINIX
and Solaris grep interprets "\|" as literal "|", and not as an alternation
as GNU grep does.  Removed such constructs introduced in f1daa0356a1d.
This fixes clang detection on MINIX.

Now we always set NGX_CC_NAME to "msvc", and additionally test compiler
version as reported by "cl" in auto/cc/msvc (the same version is also
available via the _MSC_VER define).  In particular, this approach allows
to properly check for C99 variadic macros support, which previously was
not used with MSVC versions not explicitly recognized.

Now unneeded wildcards in NGX_CC_NAME tests for msvc removed accordingly,
as well as unused wildcards for owc and icc.

The -Werror is commented out to not break builds on Linux.

New versions of icc confuse auto/cc/name due to introduced handling
of a "icc -v":

$ icc -v
icc version 12.1.3 (gcc version 4.6.0 compatibility)
$ icc -V
Intel(R) C Compiler XE for applications running on IA-32, Version 12.1.3.293 Build 20120212
Copyright (C) 1985-2012 Intel Corporation.  All rights reserved.
FOR NON-COMMERCIAL USE ONLY

See report here:
http://mailman.nginx.org/pipermail/nginx/2012-February/032177.html