macOS/Xcode no longer populate /usr/include.
Building with the compiler directly instead of using /usr/bin/c++
can result in missing headers without the -isysroot flag.

Relates: #19885

This test does not work in all environments, so add an option to
disable it.

All these expressions work the same:
  "foo"
  ".*foo.*"
  "^.*foo.*$"

This assumes that the "Intel*" expressions were meant to be "Intel.*".

The final location and name of a build-target is not determined
until generate-time. However, reading the LOCATION property from
a target is currently allowed at configure time. Apart from creating
possibly-erroneous results, this has an impact on the implementation
of cmake itself, and prevents some major cleanups from being made.

Disallow reading LOCATION from build-targets with a policy. Port some
existing uses of it in CMake itself to use the TARGET_FILE generator
expression.

BSD make doesn't use -v for printing its name and version, and so
complains on stderr that this is a bad command line option, used
in Tests/FindPackageModeMakefileTest/CMakeLists.txt .
Silence stderr to make that ugly output go away.
Patch by David Coppy.

Alex

The makefile used in the test uses $(shell ...), which is
AFAIK a GNU extension, and will probably not work e.g. with OpenBSD make.
According to the FreeBSD make manpage their make has a != assignment,
which seems to do something similar, but I don't have such a system
around for testing.
Also, the point of this test is not to write a portable makefile,
but to check whether cmake --find-package prints a correct string.

Alex

Instead of relying on that some development package is installed on the
system, now a tiny library is built, which is the searched and used
during the test.

Alex

BSD make doesn't seem to support -C, so do not use it,
According to the documentation the working directory is set
to CMAKE_CURRENT_BINARY_DIR anyway, so it should work just the same.

Alex

Alex

Alex